diff --git a/R/data.table.R b/R/data.table.R
index c05e7d0074..8cde3e3aee 100644
--- a/R/data.table.R
+++ b/R/data.table.R
@@ -820,7 +820,7 @@ replace_dot_alias = function(e) {
           if (!typeof(byval[[jj]]) %chin% ORDERING_TYPES) stop("column or expression ",jj," of 'by' or 'keyby' is type ",typeof(byval[[jj]]),". Do not quote column names. Usage: DT[,sum(colC),by=list(colA,month(colB))]")
         }
         tt = vapply_1i(byval,length)
-        if (any(tt!=xnrow)) stop("The items in the 'by' or 'keyby' list are length (",paste(tt,collapse=","),"). Each must be length ", xnrow, "; the same length as there are rows in x (after subsetting if i is provided).")
+        if (any(tt!=xnrow)) stop(gettextf("The items in the 'by' or 'keyby' list are length(s) (%s). Each must be length %d; the same length as there are rows in x (after subsetting if i is provided).", paste(tt, collapse=","), xnrow, domain='R-data.table'))
         if (is.null(bynames)) bynames = rep.int("",length(byval))
         if (length(idx <- which(!nzchar(bynames))) && !bynull) {
           # TODO: improve this and unify auto-naming of jsub and bysub
@@ -874,7 +874,7 @@ replace_dot_alias = function(e) {
             # attempt to auto-name unnamed columns
             for (jj in which(nm=="")) {
               thisq = q[[jj + 1L]]
-              if (missing(thisq)) stop("Item ", jj, " of the .() or list() passed to j is missing") #3507
+              if (missing(thisq)) stop(gettextf("Item %d of the .() or list() passed to j is missing", jj, domain="R-data.table")) #3507
               if (is.name(thisq)) nm[jj] = drop_dot(thisq)
               # TO DO: if call to a[1] for example, then call it 'a' too
             }
diff --git a/R/devel.R b/R/devel.R
index c82c62f136..8db74e47ce 100644
--- a/R/devel.R
+++ b/R/devel.R
@@ -13,7 +13,7 @@ dcf.repo = function(pkg, repo, field, type){
   idx = file(file.path(contrib.url(repo, type=type),"PACKAGES"))
   on.exit(close(idx))
   dcf = read.dcf(idx, fields=c("Package",field))
-  if (!pkg %in% dcf[,"Package"]) stop("There is no ", pkg, " package in provided repository.")
+  if (!pkg %in% dcf[,"Package"]) stop(gettextf("There is no package %s in provided repository.", pkg, domain='R-data.table'))
   dcf[dcf[,"Package"]==pkg, field][[1L]]
 }
 
diff --git a/R/last.R b/R/last.R
index 8b26b92850..abf4050b40 100644
--- a/R/last.R
+++ b/R/last.R
@@ -35,7 +35,7 @@ last = function(x, n=1L, ...) {
     }
   } else {
     if (!requireNamespace("xts", quietly=TRUE))
-      stop("'xts' class passed to data.table::last function but 'xts' is not available, you should have 'xts' installed already") # nocov
+      stop(gettextf("'xts' class passed to %s function but 'xts' is not available, you should have 'xts' installed already", "data.table::last", domain="R-data.table")) # nocov
     if (verbose)
       cat("last: using xts::last: is.xts(x)\n")
     xts::last(x, n=n, ...)
@@ -76,7 +76,7 @@ first = function(x, n=1L, ...) {
     }
   } else {
     if (!requireNamespace("xts", quietly=TRUE))
-      stop("'xts' class passed to data.table::first function but 'xts' is not available, you should have 'xts' installed already") # nocov
+      stop(gettextf("'xts' class passed to %s function but 'xts' is not available, you should have 'xts' installed already", "data.table::first", domain="R-data.table")) # nocov
     if (verbose)
       cat("first: using xts::first: is.xts(x)\n")
     xts::first(x, n=n, ...)
diff --git a/R/setkey.R b/R/setkey.R
index 5caefcf68f..fb8924b7a4 100644
--- a/R/setkey.R
+++ b/R/setkey.R
@@ -251,7 +251,7 @@ setorder = function(x, ..., na.last=FALSE)
 # na.last=FALSE here, to be consistent with data.table's default
 # as opposed to DT[order(.)] where na.last=TRUE, to be consistent with base
 {
-  if (!is.data.frame(x)) stop("x must be a data.frame or data.table.")
+  if (!is.data.frame(x)) stop("x must be a data.frame or data.table")
   cols = substitute(list(...))[-1L]
   if (identical(as.character(cols),"NULL")) return(x)
   if (length(cols)) {
@@ -357,7 +357,7 @@ CJ = function(..., sorted = TRUE, unique = FALSE)
     }
   }
   nrow = prod( vapply_1i(l, length) )  # lengths(l) will work from R 3.2.0
-  if (nrow > .Machine$integer.max) stop("Cross product of elements provided to CJ() would result in ",nrow," rows which exceeds .Machine$integer.max == ",.Machine$integer.max)
+  if (nrow > .Machine$integer.max) stop(gettextf("Cross product of elements provided to CJ() would result in %d rows which exceeds .Machine$integer.max == %d", nrow, Machine$integer.max, domain='R-data.table'))
   l = .Call(Ccj, l)
   setDT(l)
   l = setalloccol(l)  # a tiny bit wasteful to over-allocate a fixed join table (column slots only), doing it anyway for consistency since
diff --git a/R/test.data.table.R b/R/test.data.table.R
index decf1c4b3c..33752545d5 100644
--- a/R/test.data.table.R
+++ b/R/test.data.table.R
@@ -43,7 +43,7 @@ test.data.table = function(script="tests.Rraw", verbose=FALSE, pkg=".", silent=F
     # nocov start
     fn2 = paste0(fn,".bz2")
     if (!file.exists(file.path(fulldir, fn2)))
-      stop("Neither ",fn," or ",fn2," exist in ",fulldir)
+      stop(gettextf("Neither %s nor %s exist in %s",fn, fn2, fulldir, domain="R-data.table"))
     fn = fn2
     # nocov end
     # sys.source() below accepts .bz2 directly.
diff --git a/inst/po/en@quot/LC_MESSAGES/R-data.table.mo b/inst/po/en@quot/LC_MESSAGES/R-data.table.mo
index 858b4ec1be..e52bcf8faf 100644
Binary files a/inst/po/en@quot/LC_MESSAGES/R-data.table.mo and b/inst/po/en@quot/LC_MESSAGES/R-data.table.mo differ
diff --git a/inst/po/en@quot/LC_MESSAGES/data.table.mo b/inst/po/en@quot/LC_MESSAGES/data.table.mo
index 1d85d8380e..f88de8edf3 100644
Binary files a/inst/po/en@quot/LC_MESSAGES/data.table.mo and b/inst/po/en@quot/LC_MESSAGES/data.table.mo differ
diff --git a/inst/po/zh_CN/LC_MESSAGES/R-data.table.mo b/inst/po/zh_CN/LC_MESSAGES/R-data.table.mo
index f147769166..6e524b3588 100644
Binary files a/inst/po/zh_CN/LC_MESSAGES/R-data.table.mo and b/inst/po/zh_CN/LC_MESSAGES/R-data.table.mo differ
diff --git a/inst/po/zh_CN/LC_MESSAGES/data.table.mo b/inst/po/zh_CN/LC_MESSAGES/data.table.mo
index adb5351490..c5d63fb7d3 100644
Binary files a/inst/po/zh_CN/LC_MESSAGES/data.table.mo and b/inst/po/zh_CN/LC_MESSAGES/data.table.mo differ
diff --git a/inst/tests/tests.Rraw b/inst/tests/tests.Rraw
index 1eec432dd0..bc0c7b3220 100644
--- a/inst/tests/tests.Rraw
+++ b/inst/tests/tests.Rraw
@@ -13889,7 +13889,7 @@ test(1984.05, DT[ , sum(b), keyby = c, verbose = TRUE],
 test(1984.06, DT[1:3, sum(a), by=b:c], data.table(b=10:8, c=1:3, V1=1:3))
 test(1984.07, DT[, sum(a), by=call('sin',pi)], error='must evaluate to a vector or a list of vectors')
 test(1984.08, DT[, sum(a), by=as.raw(0)],           error='column or expression.*type raw')
-test(1984.09, DT[, sum(a), by=.(1,1:2)],       error='The items.*list are length [(]1,2[)].*Each must be length 10; .*rows in x.*after subsetting')
+test(1984.09, DT[, sum(a), by=.(1,1:2)],       error='The items.*list are length[(]s[)] [(]1,2[)].*Each must be length 10; .*rows in x.*after subsetting')
 options('datatable.optimize' = Inf)
 test(1984.10, DT[ , 1, by = .(a %% 2), verbose = TRUE],
      data.table(a = c(1, 0), V1 = c(1, 1)),
diff --git a/po/R-data.table.pot b/po/R-data.table.pot
index caf1686ff2..10a5b19d45 100644
--- a/po/R-data.table.pot
+++ b/po/R-data.table.pot
@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: data.table 1.12.9\n"
-"POT-Creation-Date: 2019-12-22 23:59\n"
+"POT-Creation-Date: 2019-12-29 22:35\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -403,13 +403,7 @@ msgstr ""
 msgid ". Do not quote column names. Usage: DT[,sum(colC),by=list(colA,month(colB))]"
 msgstr ""
 
-msgid "The items in the 'by' or 'keyby' list are length ("
-msgstr ""
-
-msgid "). Each must be length"
-msgstr ""
-
-msgid "; the same length as there are rows in x (after subsetting if i is provided)."
+msgid "The items in the 'by' or 'keyby' list are length(s) (%s). Each must be length %d; the same length as there are rows in x (after subsetting if i is provided)."
 msgstr ""
 
 msgid "Internal error: drop_dot passed"
@@ -418,7 +412,7 @@ msgstr ""
 msgid "items"
 msgstr ""
 
-msgid "of the .() or list() passed to j is missing"
+msgid "Item %d of the .() or list() passed to j is missing"
 msgstr ""
 
 msgid "Different branches of j expression produced different auto-named columns:"
@@ -853,10 +847,7 @@ msgstr ""
 msgid "."
 msgstr ""
 
-msgid "There is no"
-msgstr ""
-
-msgid "package in provided repository."
+msgid "There is no package %s in provided repository."
 msgstr ""
 
 msgid "'fromLast' must be TRUE or FALSE"
@@ -1324,10 +1315,7 @@ msgstr ""
 msgid "Using integer64 class columns require to have 'bit64' package installed."
 msgstr ""
 
-msgid "'xts' class passed to data.table::last function but 'xts' is not available, you should have 'xts' installed already"
-msgstr ""
-
-msgid "'xts' class passed to data.table::first function but 'xts' is not available, you should have 'xts' installed already"
+msgid "'xts' class passed to %s function but 'xts' is not available, you should have 'xts' installed already"
 msgstr ""
 
 msgid "Argument 'sort' should be logical TRUE/FALSE"
@@ -1549,9 +1537,6 @@ msgstr ""
 msgid "New parallel sort has not been implemented for vectors containing NA values so far. Using one thread."
 msgstr ""
 
-msgid "x must be a data.frame or data.table."
-msgstr ""
-
 msgid "x must be a data.frame or data.table"
 msgstr ""
 
@@ -1573,10 +1558,7 @@ msgstr ""
 msgid "is non-atomic, which can't be sorted; try setting sorted = FALSE"
 msgstr ""
 
-msgid "Cross product of elements provided to CJ() would result in"
-msgstr ""
-
-msgid "rows which exceeds .Machine$integer.max =="
+msgid "Cross product of elements provided to CJ() would result in %d rows which exceeds .Machine$integer.max == %d"
 msgstr ""
 
 msgid "x and y must both be data.tables"
@@ -1669,10 +1651,7 @@ msgstr ""
 msgid "script must end with '.Rraw'. If a file ending '.Rraw.bz2' exists, that will be found and used."
 msgstr ""
 
-msgid "Neither"
-msgstr ""
-
-msgid "exist in"
+msgid "Neither %s nor %s exist in %s"
 msgstr ""
 
 msgid "Failed after test"
diff --git a/po/R-zh_CN.po b/po/R-zh_CN.po
index 7afdcdae16..e74646eb14 100644
--- a/po/R-zh_CN.po
+++ b/po/R-zh_CN.po
@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: data.table 1.12.5\n"
-"POT-Creation-Date: 2019-12-22 23:59\n"
+"POT-Creation-Date: 2019-12-29 22:35\n"
 "PO-Revision-Date: 2019-11-16 18:37+0800\n"
 "Last-Translator: Xianying Tan <shrektan@126.com>\n"
 "Language-Team: Mandarin\n"
@@ -9,6 +9,7 @@ msgstr ""
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"
+"Plural-Forms: nplurals=1; plural=0;\n"
 
 msgid "data.table package loaded. When developing don't load package"
 msgstr "data.table包已载入, 开发时无需载入"
@@ -153,7 +154,7 @@ msgid "; expecting length 2."
 msgstr "；其长度应为 2。"
 
 msgid "c"
-msgstr ""
+msgstr "c"
 
 msgid "Perhaps you meant %s?"
 msgstr "或许你想用的是 %s？"
@@ -165,7 +166,7 @@ msgid "the second element should be the upper bound(s)."
 msgstr "第二个元素应为上界。"
 
 msgid "x."
-msgstr ""
+msgstr "x."
 
 msgid "is type"
 msgstr "的类型为"
@@ -174,7 +175,7 @@ msgid "which is not supported by data.table join"
 msgstr "，该类型无法用于 data.table 的联接"
 
 msgid "i."
-msgstr ""
+msgstr "i."
 
 msgid "Attempting roll join on factor column when joining x."
 msgstr "试图滚动联接（roll join）因子类型（factor）的列，这发生于将 x."
@@ -422,16 +423,16 @@ msgid "Attempting to do natural join but no common columns in provided tables"
 msgstr "尝试进行自然连接然而并没有找到表格中相同的列"
 
 msgid "Internal error. Cannot by=.EACHI when joining to a secondary key, yet"
-msgstr ""
+msgstr "内部错误：目前尚无法对次键使用by=.EACH命令"
 
 msgid "Internal error. irows has length in by=.EACHI"
-msgstr ""
+msgstr "内部错误：by=.EACHI 中 irows 有长度"
 
 msgid "logical error. i is not a data.table, but 'on' argument is provided."
-msgstr ""
+msgstr "逻辑错误。当 i 并非一个 data.table时，不应提供'on'参数"
 
 msgid "i has evaluated to type"
-msgstr ""
+msgstr "i 运算结果为类型"
 
 msgid ". Expecting logical, integer or double."
 msgstr "。期望布尔类型，整型或浮点型。"
@@ -540,43 +541,35 @@ msgid ""
 ". Do not quote column names. Usage: DT[,sum(colC),by=list(colA,month(colB))]"
 msgstr "。请勿引用列名。用法：DT[,sum(colC),by=list(colA,month(colB))]"
 
-msgid "The items in the 'by' or 'keyby' list are length ("
-msgstr "'by' 或 'keyby' 列表中的元素长度为（"
-
-msgid "). Each must be length"
-msgstr ""
-
 msgid ""
-"; the same length as there are rows in x (after subsetting if i is provided)."
-msgstr ""
+"The items in the 'by' or 'keyby' list are length(s) (%s). Each must be "
+"length %d; the same length as there are rows in x (after subsetting if i is "
+"provided)."
+msgstr "在'by'或'keyby'列表中的项长度为 %s。每一项的长度须均为%d，即应与 x （或经 i 筛选后的子集）中所包含行数相同。"
 
 msgid "Internal error: drop_dot passed"
-msgstr ""
+msgstr "内部错误：drop_dot 传入的参数有"
 
 msgid "items"
-msgstr ""
+msgstr "项"
 
-msgid "of the .() or list() passed to j is missing"
-msgstr ""
+msgid "Item %d of the .() or list() passed to j is missing"
+msgstr "传递给j的 .() 或 list()中第%d项缺失"
 
-msgid ""
-"Different branches of j expression produced different auto-named columns:"
-msgstr ""
+msgid "Different branches of j expression produced different auto-named columns:"
+msgstr "j表达式中的不同分支自动生成的列名不同："
 
 msgid "%s!=%s"
-msgstr ""
+msgstr "%s!=%s"
 
 msgid "; using the most \"last\" names"
-msgstr ""
+msgstr "；将使用最晚生成的名字"
 
-msgid ""
-"When .SDcols is a function, it is applied to each column; the output of this "
-"function must be a non-missing boolean scalar signalling inclusion/exclusion "
-"of the column. However, these conditions were not met for:"
-msgstr ""
+msgid "When .SDcols is a function, it is applied to each column; the output of this function must be a non-missing boolean scalar signalling inclusion/exclusion of the column. However, these conditions were not met for:"
+msgstr "当传入 .SDcols 的参数为一个方程时，该方程将应用于每一列，并须返回单个非缺失值的布尔值指示该列是否应当被包含/排除。然而上述条件对如下列并不满足："
 
 msgid ".SDcols missing at the following indices:"
-msgstr ""
+msgstr ".SDcols 的如下位置为缺失值："
 
 msgid ".SDcols is numeric but has both +ve and -ve indices"
 msgstr ".SDcols 为数值，但同时具有 +ve 和 -ve 索引"
@@ -1061,7 +1054,7 @@ msgstr ""
 "（length）：频率（frequency））是："
 
 msgid "%s:%d"
-msgstr ""
+msgstr "%s:%d"
 
 msgid "The first entry with fewer than"
 msgstr "第一个长度少于"
@@ -1139,94 +1132,79 @@ msgid ". Only allowed operators are"
 msgstr "。只有这些操作符是有效的"
 
 msgid "."
-msgstr ""
-
-msgid "There is no"
-msgstr ""
+msgstr "."
 
-msgid "package in provided repository."
-msgstr ""
+msgid "There is no package %s in provided repository."
+msgstr "所提供的资料库中不含包%s"
 
 msgid "'fromLast' must be TRUE or FALSE"
-msgstr ""
+msgstr "'fromLast' 必须为 TRUE 或 FALSE"
 
 msgid "x must be an atomic vector or data.frames/data.tables"
-msgstr ""
+msgstr "x 必须是原子向量或data.frame/data.table"
 
 msgid "Using '"
-msgstr ""
+msgstr "使用 '"
 
 msgid "' as value column. Use 'value.var' to override"
-msgstr ""
+msgstr "' 作为 value 列。可使用 'value.var' 修改"
 
 msgid "The dcast generic in data.table has been passed a"
-msgstr ""
+msgstr "data.table 中的 dcast 泛型函数被传递了"
 
-msgid ""
-", but data.table::dcast currently only has a method for data.tables. Please "
-"confirm your input is a data.table, with setDT("
-msgstr ""
+msgid ", but data.table::dcast currently only has a method for data.tables. Please confirm your input is a data.table, with setDT("
+msgstr "，但目前 data.table::dcast 仅提供了针对 data.table 的方法。您可通过如下两种方法确保您的输入为一个 data.table对象，即setDT("
 
 msgid ") or as.data.table("
-msgstr ""
+msgstr ") 或 as.data.table("
 
-msgid ""
-"). If you intend to use a reshape2::dcast, try installing that package "
-"first, but do note that reshape2 is deprecated and you should be migrating "
-"your code away from using it."
-msgstr ""
+msgid "). If you intend to use a reshape2::dcast, try installing that package first, but do note that reshape2 is deprecated and you should be migrating your code away from using it."
+msgstr ")。若您想使用reshape2::dcast，尝试先安装reshape2。但请注意reshape2已经不推荐使用，您应修改您的代码以不再使用它。"
 
-msgid ""
-"and will attempt to redirect to the reshape2::dcast; please note that "
-"reshape2 is deprecated, and this redirection is now deprecated as well. "
-"Please do this redirection yourself like reshape2::dcast("
-msgstr ""
+msgid "and will attempt to redirect to the reshape2::dcast; please note that reshape2 is deprecated, and this redirection is now deprecated as well. Please do this redirection yourself like reshape2::dcast("
+msgstr "，将尝试重定向到reshape2::dcast。请注意reshape2已经不推荐使用，故该重定向目前也不推荐使用。请手动执行该重定向，如reshape2::dcast("
 
 msgid "). In the next version, this warning will become an error."
-msgstr ""
+msgstr ")。在下一个版本中，此警告将变成为错误。"
 
-msgid ""
-"Invalid formula. Cast formula should be of the form LHS ~ RHS, for e.g., a + "
-"b ~ c."
-msgstr ""
+msgid "Invalid formula. Cast formula should be of the form LHS ~ RHS, for e.g., a + b ~ c."
+msgstr "无效的公式。所转换的公式的形式应为LHS ~ RHS，如a + b ~ c。"
 
 msgid "data.table to cast must have unique column names"
-msgstr ""
+msgstr "要转换的data.table必须具有唯一的列名"
 
 msgid "value.var values ["
-msgstr ""
+msgstr "value.var 的值 ["
 
 msgid "] are not found in 'data'."
-msgstr ""
+msgstr "] 无法在 'data' 中找到"
 
-msgid ""
-"When 'fun.aggregate' and 'value.var' are both lists, 'value.var' must be "
-"either of length =1 or =length(fun.aggregate)."
-msgstr ""
+msgid "When 'fun.aggregate' and 'value.var' are both lists, 'value.var' must be either of length =1 or =length(fun.aggregate)."
+msgstr "当 'fun.aggregate' 和 'value.var' 同为 list时, 'value.var' 的长度必须为 1 或 length(fun.aggregate)。"
 
 msgid "'data' must be a data.table."
-msgstr ""
+msgstr "'data' 必须为 data.table"
 
 msgid "'drop' must be logical TRUE/FALSE"
-msgstr ""
+msgstr "'drop' 必须为逻辑 TRUE/FALSE"
 
 msgid "Column ["
-msgstr ""
+msgstr "列 ["
 
 msgid "] not found or of unknown type."
-msgstr ""
+msgstr "] 无法找到或其类型未知。"
 
 msgid "Columns specified in formula can not be of type list"
-msgstr ""
+msgstr "在formula中指定的列不应为列表类型"
 
 msgid "Can not cast an empty data.table"
-msgstr ""
+msgstr "无法转换一个空的data.table"
 
 msgid "Aggregate function missing, defaulting to 'length'"
-msgstr ""
+msgstr "聚合函数缺失，将默认采用'length'"
 
 msgid "Internal error -- empty rhsnames in dcast; please report"
-msgstr ""
+msgstr "内部错误：dcast 中 rhsnames 为空；请报告"
 
 msgid "The melt generic in data.table has been passed a"
 msgstr "data.table 中的 melt 泛型函数被传递了"
@@ -1498,10 +1476,10 @@ msgid "' has size 0. Returning a NULL"
 msgstr "' 的大小为0. 返回一个NULL"
 
 msgid "data.table"
-msgstr ""
+msgstr "data.table"
 
 msgid "data.frame"
-msgstr ""
+msgstr "data.frame"
 
 msgid ""
 "To read gz and bz2 files directly, fread() requires 'R.utils' package which "
@@ -1583,7 +1561,7 @@ msgid "Encountered <"
 msgstr "遇到 <"
 
 msgid "..."
-msgstr ""
+msgstr "..."
 
 msgid "> at the first"
 msgstr "> 在第一个"
@@ -1674,7 +1652,7 @@ msgid "warning"
 msgstr "警告"
 
 msgid ":"
-msgstr "："
+msgstr ":"
 
 msgid "so the column has been left as type '"
 msgstr "所以该列已经被保存为类型"
@@ -1682,12 +1660,15 @@ msgstr "所以该列已经被保存为类型"
 msgid ""
 "key argument of data.table() must be a character vector naming columns (NB: "
 "col.names are applied before this)"
-msgstr "data.table()的关键参数必须是字符向量命名的列（NB:col.names在这之前被使用过）"
+msgstr ""
+"data.table()的关键参数必须是字符向量命名的列（NB:col.names在这之前被使用过）"
 
 msgid ""
 "index argument of data.table() must be a character vector naming columns "
 "(NB: col.names are applied before this)"
-msgstr "data.table()的index参数必须是字符向量命名的列（NB:参数col.names在这之前被使用过）"
+msgstr ""
+"data.table()的index参数必须是字符向量命名的列（NB:参数col.names在这之前被使用"
+"过）"
 
 msgid "dateTimeAs must be a single string"
 msgstr "dataTimeAs 必须是单个字符串"
@@ -1797,15 +1778,8 @@ msgid ""
 "Using integer64 class columns require to have 'bit64' package installed."
 msgstr "要在列中使用 integer64 类，需要先安装 'bit64' 包。"
 
-msgid ""
-"'xts' class passed to data.table::last function but 'xts' is not available, "
-"you should have 'xts' installed already"
-msgstr ""
-
-msgid ""
-"'xts' class passed to data.table::first function but 'xts' is not available, "
-"you should have 'xts' installed already"
-msgstr ""
+msgid "'xts' class passed to %s function but 'xts' is not available, you should have 'xts' installed already"
+msgstr "'xts'类对象传递给了%s方程，但是'xts'包不可用。您应首先安装'xts'包"
 
 msgid "Argument 'sort' should be logical TRUE/FALSE"
 msgstr "参数 'sort' 应为逻辑值 TRUE 或 FALSE"
@@ -2108,64 +2082,49 @@ msgstr ""
 "table或者data.frame"
 
 msgid "Internal code should not be being called on type double"
-msgstr ""
-
-msgid ""
-"Input is not a vector of type double. New parallel sort has only been done "
-"for double vectors so far. Using one thread."
-msgstr ""
+msgstr "内部代码不应被调用给双精度类型"
 
-msgid ""
-"New parallel sort has not been implemented for decreasing=TRUE so far. Using "
-"one thread."
-msgstr ""
+msgid "Input is not a vector of type double. New parallel sort has only been done for double vectors so far. Using one thread."
+msgstr "输入一个并非双精度类型的向量。目前新的并行排序方法仅可应用于双精确度向量。将使用单线程进行计算"
 
-msgid ""
-"New parallel sort has not been implemented for vectors containing NA values "
-"so far. Using one thread."
-msgstr ""
+msgid "New parallel sort has not been implemented for decreasing=TRUE so far. Using one thread."
+msgstr "目前新的并行排序方法尚无法在decreasing=TRUE的条件下使用。将使用单线程进行计算。"
 
-msgid "x must be a data.frame or data.table."
-msgstr ""
+msgid "New parallel sort has not been implemented for vectors containing NA values so far. Using one thread."
+msgstr "目前新的并行排序方法尚无法用于包含缺失值的向量。将使用单线程。"
 
 msgid "x must be a data.frame or data.table"
-msgstr ""
+msgstr "x 必须为 data.frame 或 data.table"
 
 msgid "na.last must be logical TRUE/FALSE"
-msgstr ""
+msgstr "na.last 必须为逻辑 TRUE/FALSE"
 
-msgid ""
-"cols is not a character vector. Please see further information in ?setorder."
-msgstr ""
+msgid "cols is not a character vector. Please see further information in ?setorder."
+msgstr "cols并非一个字符向量。请参考 ?setorder以获得更多信息。"
 
-msgid ""
-"cols is a character vector of zero length. Use NULL instead, or wrap with "
-"suppressWarnings() to avoid this warning."
-msgstr ""
+msgid "cols is a character vector of zero length. Use NULL instead, or wrap with suppressWarnings() to avoid this warning."
+msgstr "cols为一长度为零的字符向量。请使用NULL代替，或将本函数使用suppressWarnings()包裹以阻止该警告。"
 
 msgid "' which is not supported for ordering currently."
-msgstr ""
+msgstr "'，该类型目前尚不支持排序。"
 
 msgid "'sorted' is TRUE but element"
-msgstr ""
+msgstr "'sorted' 为 TRUE 但元素"
 
 msgid "is non-atomic, which can't be sorted; try setting sorted = FALSE"
-msgstr ""
+msgstr "并非原子类型，无法排序。请尝试使用 sorted=FALSE"
 
-msgid "Cross product of elements provided to CJ() would result in"
-msgstr ""
-
-msgid "rows which exceeds .Machine$integer.max =="
-msgstr ""
+msgid "Cross product of elements provided to CJ() would result in %d rows which exceeds .Machine$integer.max == %d"
+msgstr "CJ()中元素的叉积将产生 %d 行，已超过 .Machine$integer.max == %d"
 
 msgid "x and y must both be data.tables"
-msgstr ""
+msgstr "x 和 y 均需为 data.table"
 
 msgid "length(by.x) != length(by.y)"
-msgstr ""
+msgstr "length(by.x) != length(by.y)"
 
 msgid "When x's column ('"
-msgstr ""
+msgstr "当 x 的列 ('"
 
 msgid "') is character, the corresponding column in y ('"
 msgstr "') 是字符，y 中相应的列 ('"
@@ -2264,17 +2223,14 @@ msgstr ""
 "脚本文件名必须以 '.Rraw' 结尾。如果以 'Rraw.bz2' 结尾的文件存在，其也将被使"
 "用。"
 
-msgid "Neither"
-msgstr ""
-
-msgid "exist in"
-msgstr "均不存在于文件夹"
+msgid "Neither %s nor %s exist in %s"
+msgstr "%3$s 中 %1$s 也 %2$s 不存在"
 
 msgid "Failed after test"
-msgstr ""
+msgstr "错误出现于测试"
 
 msgid "before the next test() call in"
-msgstr ""
+msgstr "后，先于下一调用test()于"
 
 msgid "out of"
 msgstr "总数为"
@@ -2335,10 +2291,10 @@ msgid "l not type list"
 msgstr "l并非列表（list）类型"
 
 msgid "Argument 'nan' must be length 1"
-msgstr ""
+msgstr "参数 'nan' 的长度必须为 1"
 
 msgid "Argument 'nan' must be NA or NaN"
-msgstr ""
+msgstr "参数 'nan' 必须为 NA 或 NaN"
 
 msgid "x not boolean"
 msgstr "x并非布尔值"
@@ -2380,14 +2336,4 @@ msgstr "以下的列并非数值类型，将被忽略："
 
 msgid "%d variable not shown: %s\n"
 msgid_plural "%d variables not shown: %s\n"
-msgstr[0] ""
-msgstr[1] ""
-
-#~ msgid "in"
-#~ msgstr "在"
-
-#~ msgid "on"
-#~ msgstr "在"
-
-#~ msgid ". ["
-#~ msgstr ". ["
+msgstr[0] "%d变量没显示: %s\n"
diff --git a/po/data.table.pot b/po/data.table.pot
index 5041a04c94..a826bab881 100644
--- a/po/data.table.pot
+++ b/po/data.table.pot
@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: data.table 1.12.9\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2019-12-23 00:00+0800\n"
+"POT-Creation-Date: 2019-12-30 01:24+0800\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -1715,14 +1715,6 @@ msgstr ""
 msgid "  0/1 column will be read as %s\n"
 msgstr ""
 
-#: fread.c:1158
-msgid "boolean"
-msgstr ""
-
-#: fread.c:1158
-msgid "integer"
-msgstr ""
-
 #: fread.c:1166
 #, c-format
 msgid "sep == quote ('%c') is not allowed"
@@ -2159,14 +2151,6 @@ msgid ""
 "first and only row\n"
 msgstr ""
 
-#: fread.c:1774
-msgid "true"
-msgstr ""
-
-#: fread.c:1774
-msgid "false"
-msgstr ""
-
 #: fread.c:1774
 msgid " no"
 msgstr ""
@@ -3138,16 +3122,9 @@ msgstr ""
 msgid "env is not an environment"
 msgstr ""
 
-#: gsumm.c:45
-msgid "o is not an integer vector"
-msgstr ""
-
-#: gsumm.c:46
-msgid "f is not an integer vector"
-msgstr ""
-
-#: gsumm.c:47
-msgid "l is not an integer vector"
+#: gsumm.c:45 gsumm.c:46 gsumm.c:47
+#, c-format
+msgid "%s is not an integer vector"
 msgstr ""
 
 #: gsumm.c:56
@@ -3218,9 +3195,10 @@ msgstr ""
 msgid "This gsum took (narm=%s) ... "
 msgstr ""
 
-#: gsumm.c:350 gsumm.c:606
+#: gsumm.c:350 gsumm.c:606 gsumm.c:693 gsumm.c:812 gsumm.c:955 gsumm.c:1005
+#: gsumm.c:1085 gsumm.c:1176 gsumm.c:1266 gsumm.c:1409
 #, c-format
-msgid "nrow [%d] != length(x) [%d] in gsum"
+msgid "nrow [%d] != length(x) [%d] in %s"
 msgstr ""
 
 #: gsumm.c:404
@@ -3291,11 +3269,6 @@ msgstr ""
 msgid "min is not meaningful for factors."
 msgstr ""
 
-#: gsumm.c:693
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gmin"
-msgstr ""
-
 #: gsumm.c:717 gsumm.c:850
 msgid ""
 "No non-missing values found in at least one group. Coercing to numeric type "
@@ -3337,11 +3310,6 @@ msgstr ""
 msgid "max is not meaningful for factors."
 msgstr ""
 
-#: gsumm.c:812
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gmax"
-msgstr ""
-
 #: gsumm.c:930
 msgid ""
 "No non-missing values found in at least one group. Returning '-Inf' for such "
@@ -3372,11 +3340,6 @@ msgstr ""
 msgid "median is not meaningful for factors."
 msgstr ""
 
-#: gsumm.c:955
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gmedian"
-msgstr ""
-
 #: gsumm.c:992
 #, c-format
 msgid ""
@@ -3385,11 +3348,6 @@ msgid ""
 "optimize=1)"
 msgstr ""
 
-#: gsumm.c:1005
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gtail"
-msgstr ""
-
 #: gsumm.c:1073
 #, c-format
 msgid ""
@@ -3397,11 +3355,6 @@ msgid ""
 "tail(.) or turn off GForce optimization using options(datatable.optimize=1)"
 msgstr ""
 
-#: gsumm.c:1085 gsumm.c:1176
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in ghead"
-msgstr ""
-
 #: gsumm.c:1153
 #, c-format
 msgid ""
@@ -3450,11 +3403,6 @@ msgstr ""
 msgid "var/sd is not meaningful for factors."
 msgstr ""
 
-#: gsumm.c:1266
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gvar"
-msgstr ""
-
 #: gsumm.c:1382
 #, c-format
 msgid ""
@@ -3481,11 +3429,6 @@ msgstr ""
 msgid "prod is not meaningful for factors."
 msgstr ""
 
-#: gsumm.c:1409
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gprod"
-msgstr ""
-
 #: gsumm.c:1411
 #, c-format
 msgid "Unable to allocate %d * %d bytes for gprod"
diff --git a/po/zh_CN.po b/po/zh_CN.po
index 3508a583f9..6a95727f07 100644
--- a/po/zh_CN.po
+++ b/po/zh_CN.po
@@ -2,7 +2,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: data.table 1.12.5\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2019-12-23 00:00+0800\n"
+"POT-Creation-Date: 2019-12-30 01:24+0800\n"
 "PO-Revision-Date: 2019-11-18 00:26-04\n"
 "Last-Translator: Yuhang Chen <yuhangchen0802@gmail.com>\n"
 "Language-Team: Mandarin\n"
@@ -181,7 +181,7 @@ msgstr "为所有的%d行赋值\n"
 msgid ""
 "Coerced i from numeric to integer. Please pass integer for efficiency; e.g., "
 "2L rather than 2"
-msgstr ""
+msgstr "将i由数值型强制转换为整数型。请直接传入整数以提高效率，如传入2L而非2"
 
 #: assign.c:323
 #, c-format
@@ -797,7 +797,7 @@ msgstr "内部错误: opArg 不是一个长度为 on 的整数向量"
 
 #: bmerge.c:96
 msgid "Internal error: nqgrpArg must be an integer vector"
-msgstr ""
+msgstr "内部错误：nqgrpArg 必须为一个整数向量"
 
 #: bmerge.c:102
 msgid "Intrnal error: nqmaxgrpArg is not a positive length-1 integer vector"
@@ -1015,16 +1015,16 @@ msgstr "length(iSD)[%d] != length(jiscols)[%d]"
 #: dogroups.c:92
 #, c-format
 msgid "length(xSD)[%d] != length(xjiscols)[%d]"
-msgstr ""
+msgstr "length(xSD)[%d] != length(xjiscols)[%d]"
 
 #: dogroups.c:155 dogroups.c:184
 msgid "Internal error. Type of column should have been checked by now"
-msgstr ""
+msgstr "内部错误：至此列的类型应已经被检查完成"
 
 #: dogroups.c:273
 #, c-format
 msgid "j evaluates to type '%s'. Must evaluate to atomic vector or list."
-msgstr ""
+msgstr "j的运算结果为'%s'类型。其运算结果必须为原子向量或列表。"
 
 #: dogroups.c:281
 msgid ""
@@ -1125,7 +1125,7 @@ msgstr "dogroups: 从 %d 列增加至 %d 列\n"
 #: dogroups.c:387
 #, c-format
 msgid "dogroups: length(ans)[%d]!=ngrpcols[%d]+njval[%d]"
-msgstr ""
+msgstr "dogroups: length(ans)[%d]!=ngrpcols[%d]+njval[%d]"
 
 #: dogroups.c:420
 #, c-format
@@ -1612,7 +1612,7 @@ msgstr ""
 #: forder.c:561
 #, c-format
 msgid "Column %d passed to [f]order is type '%s', not yet supported."
-msgstr ""
+msgstr "传递给 [f]order 的第%d列为 '%s'类型，目前尚不支持。"
 
 #: forder.c:714
 msgid "Internal error: column not supported, not caught earlier"
@@ -1621,7 +1621,7 @@ msgstr "内部错误：列有不支持类型，未被前置识别"
 #: forder.c:722
 #, c-format
 msgid "nradix=%d\n"
-msgstr ""
+msgstr "nradix=%d\n"
 
 #: forder.c:728
 #, c-format
@@ -1641,7 +1641,7 @@ msgstr "定时块 %2d%s = %8.3f   %8d\n"
 #: forder.c:797
 #, c-format
 msgid "stat[%03d]==%20<PRIu64>\n"
-msgstr ""
+msgstr "stat[%03d]==%20<PRIu64>\n"
 
 #: forder.c:1053
 #, c-format
@@ -1740,7 +1740,7 @@ msgstr "内部错误：参数 'cols' 关于 CanyNA 是 '%s' 类型而不是'inte
 #, c-format
 msgid ""
 "Internal error in line %d of fread.c, please report on data.table GitHub:  "
-msgstr ""
+msgstr "fread.c中%d行出现内部错误，请在 data.table 的 GitHub中提交报告："
 
 #: fread.c:147
 #, c-format
@@ -1811,11 +1811,11 @@ msgstr "未提供 NAstrings \n"
 
 #: fread.c:1146
 msgid "  NAstrings = ["
-msgstr ""
+msgstr "  NAstrings = ["
 
 #: fread.c:1149
 msgid "]\n"
-msgstr ""
+msgstr "]\n"
 
 #: fread.c:1151
 msgid "  One or more of the NAstrings looks like a number.\n"
@@ -1845,14 +1845,6 @@ msgstr "显示进程  %d\n"
 msgid "  0/1 column will be read as %s\n"
 msgstr " 0/1 列被读取为  %s\n"
 
-#: fread.c:1158
-msgid "boolean"
-msgstr ""
-
-#: fread.c:1158
-msgid "integer"
-msgstr ""
-
 #: fread.c:1166
 #, c-format
 msgid "sep == quote ('%c') is not allowed"
@@ -2199,11 +2191,11 @@ msgstr "采样跳点数 = %d 因为"
 #: fread.c:1649
 #, c-format
 msgid "nrow limit (%<PRIu64>) supplied\n"
-msgstr ""
+msgstr "指定了nrow 的最大值 (%<PRIu64>) \n"
 
 #: fread.c:1650
 msgid "jump0size==0\n"
-msgstr ""
+msgstr "jump0size==0\n"
 
 #: fread.c:1651
 #, c-format
@@ -2222,21 +2214,21 @@ msgstr "第%5$d个跳点所找到的第%4$d行，该行字段过于%1$s(%2$d/%3$
 
 #: fread.c:1690
 msgid "few"
-msgstr ""
+msgstr "少"
 
 #: fread.c:1690
 msgid "many"
-msgstr ""
+msgstr "多"
 
 #: fread.c:1690
 msgid ""
 "Most likely this jump landed awkwardly so type bumps here will be skipped."
-msgstr ""
+msgstr "很有可能这一跳点的位置并不合适，因此此处的类型转换将被跳过。"
 
 #: fread.c:1716
 #, c-format
 msgid "  Type codes (jump %03d)    : %s  Quote rule %d\n"
-msgstr ""
+msgstr " 类型码（跳点 %03d）   : %s  引用规则 %d\n"
 
 #: fread.c:1729
 #, c-format
@@ -2282,10 +2274,12 @@ msgid ""
 "setnames() afterwards if this guess is not correct, or fix the file write "
 "command that created the file to create a valid file."
 msgstr ""
+"作为第一列，并被用于猜测行名或索引。若上述猜测不正确，可在后续使用setnames()"
+"进行修改，或修复用于生成该文件的文件写入命令以生成有效的文件。"
 
 #: fread.c:1747
 msgid "s at the end."
-msgstr ""
+msgstr "到结尾处"
 
 #: fread.c:1749
 msgid ""
@@ -2314,17 +2308,9 @@ msgid ""
 "first and only row\n"
 msgstr " 参数'header' 被设置为%s， 因为唯一的一行包含 %s 个字段\n"
 
-#: fread.c:1774
-msgid "true"
-msgstr ""
-
-#: fread.c:1774
-msgid "false"
-msgstr ""
-
 #: fread.c:1774
 msgid " no"
-msgstr ""
+msgstr "0"
 
 #: fread.c:1777
 msgid ""
@@ -2341,7 +2327,7 @@ msgstr "参数 'header' 被设置为false，因为部分字段的首行不为字
 #: fread.c:1795
 #, c-format
 msgid "  Type codes (first row)   : %s  Quote rule %d\n"
-msgstr ""
+msgstr " 类型码（第一行）   : %s  引用规则 %d\n"
 
 #: fread.c:1804
 #, c-format
@@ -2365,7 +2351,7 @@ msgstr "  已使用了 %2$d个跳点抽样 %1$<PRIu64> 行(处理了字段间的
 #, c-format
 msgid ""
 "  Bytes from first data row on line %d to the end of last row: %<PRIu64>\n"
-msgstr ""
+msgstr " 从第一个数据行(%d)到最后一行的字节: %<PRIu64>\n"
 
 #: fread.c:1819
 #, c-format
@@ -2383,6 +2369,8 @@ msgid ""
 "  Initial alloc = %<PRIu64> rows (%<PRIu64> + %d%%) using bytes/"
 "max(mean-2*sd,min) clamped between [1.1*estn, 2.0*estn]\n"
 msgstr ""
+"为 %<PRIu64> 行 (%<PRIu64> + %d%%)分配初始内存，大小为字节数/max(mean-2*sd,"
+"min)，并确保该数值落于区间[1.1*estn, 2.0*estn]中\n"
 
 #: fread.c:1825
 #, c-format
@@ -2462,7 +2450,7 @@ msgstr "  jumps=[%d..%d)，chunk_size=%<PRIu64>，total_size=%<PRIu64>\n"
 #: fread.c:2005
 #, c-format
 msgid "Internal error: Master thread is not thread 0 but thread %d.\n"
-msgstr ""
+msgstr "内部错误：主线程并非线程0而是线程%d\n"
 
 #: fread.c:2213
 #, c-format
@@ -2478,7 +2466,7 @@ msgstr ""
 msgid ""
 "Internal error: invalid head position. jump=%d, headPos=%p, thisJumpStart="
 "%p, sof=%p"
-msgstr ""
+msgstr "内部错误：head 位置无效。jump=%d, headPos=%p, thisJumpStart=%p, sof=%p"
 
 #: fread.c:2335
 #, c-format
@@ -3104,7 +3092,7 @@ msgstr "x 目前必须是双精度 ('double') 类型的向量"
 #: fsort.c:122
 #, c-format
 msgid "nth=%d, nBatch=%d\n"
-msgstr ""
+msgstr "nth=%d, nBatch=%d\n"
 
 #: fsort.c:156
 #, c-format
@@ -3127,12 +3115,15 @@ msgstr "无法分配工作内存"
 #: fsort.c:177
 #, c-format
 msgid ""
-"counts is %dMB (%d pages per nBatch=%d, batchSize=%<PRIu64>, lastBatchSize=%<PRIu64>)\n"
-msgstr "counts为%dMB (每个nBatch中的%d页=%d, batchSize=%<PRIu64>, lastBatchSize=%<PRIu64>)\n"
+"counts is %dMB (%d pages per nBatch=%d, batchSize=%<PRIu64>, lastBatchSize="
+"%<PRIu64>)\n"
+msgstr ""
+"counts为%dMB (每个nBatch中的%d页=%d, batchSize=%<PRIu64>, lastBatchSize="
+"%<PRIu64>)\n"
 
 #: fsort.c:231
 msgid "Internal error: counts[nBatch-1][MSBsize-1] != length(x)"
-msgstr "内部错误：counts[nBatch-1][MSBsize-1] 不等于 length(x)"
+msgstr "内部错误：counts[nBatch-1][MSBsize-1] != length(x)"
 
 #: fsort.c:247
 msgid "Top 5 MSB counts: "
@@ -3190,11 +3181,12 @@ msgstr "... "
 #, c-format
 msgid ""
 "\n"
-"args.doRowNames=%d args.rowNames=%d doQuote=%d args.nrow=%<PRId64> args.ncol=%d "
-"eolLen=%d\n"
-msgstr "\n"
-"args.doRowNames=%d args.rowNames=%d doQuote=%d args.nrow=%<PRId64> args.ncol=%d "
-"eolLen=%d\n"
+"args.doRowNames=%d args.rowNames=%d doQuote=%d args.nrow=%<PRId64> args.ncol="
+"%d eolLen=%d\n"
+msgstr ""
+"\n"
+"args.doRowNames=%d args.rowNames=%d doQuote=%d args.nrow=%<PRId64> args.ncol="
+"%d eolLen=%d\n"
 
 #: fwrite.c:664
 #, c-format
@@ -3212,8 +3204,9 @@ msgid ""
 "%s: '%s'. Failed to open existing file for writing. Do you have write "
 "permission to it? Is this Windows and does another process such as Excel "
 "have it open?"
-msgstr "%s: '%s'. 无法打开一斤存在的文件进行写入.你是否对该文件有写入权限？"
-"这是Windows系统？是否有Excel之类的进程已经打开了该文件？"
+msgstr ""
+"%s: '%s'. 无法打开一斤存在的文件进行写入.你是否对该文件有写入权限？这是"
+"Windows系统？是否有Excel之类的进程已经打开了该文件？"
 
 #: fwrite.c:692
 #, c-format
@@ -3221,8 +3214,9 @@ msgid ""
 "%s: '%s'. Unable to create new file for writing (it does not exist already). "
 "Do you have permission to write here, is there space on the disk and does "
 "the path exist?"
-msgstr "%s: '%s'. 无法创建新的文件进行写入（文件不存在）"
-"你是否对此有写入权限？磁盘上是否有空间以及路径是否存在？"
+msgstr ""
+"%s: '%s'. 无法创建新的文件进行写入（文件不存在）你是否对此有写入权限？磁盘上"
+"是否有空间以及路径是否存在？"
 
 #: fwrite.c:700
 #, c-format
@@ -3291,7 +3285,8 @@ msgstr "请将此消息上方和下方的全部输出结果一起提交到data.t
 msgid ""
 "Please retry fwrite() with verbose=TRUE and include the full output with "
 "your data.table bug report."
-msgstr "请使用verbose=TRUE重试fwrite()，并将完整的输出提交到data.table的bug report中"
+msgstr ""
+"请使用verbose=TRUE重试fwrite()，并将完整的输出提交到data.table的bug report中"
 
 #: fwriteR.c:41
 msgid "Internal error: col passed to getMaxCategLen is missing levels"
@@ -3307,9 +3302,9 @@ msgid ""
 "Row %d of list column is type '%s' - not yet implemented. fwrite() can write "
 "list columns containing items which are atomic vectors of type logical, "
 "integer, integer64, double, complex and character."
-msgstr "列表页行%d的类型是'%s' - 尚未实施. fwrite()可以写入"
-"包含逻辑类型原子向量项目的列表页，"
-"整数，整数64，双精度，复数和字符"
+msgstr ""
+"列表页行%d的类型是'%s' - 尚未实施. fwrite()可以写入包含逻辑类型原子向量项目的"
+"列表页，整数，整数64，双精度，复数和字符"
 
 #: fwriteR.c:103
 #, c-format
@@ -3340,7 +3335,9 @@ msgstr "列%d的类型是'%s' - 尚未在fwrite中实施"
 msgid ""
 "No list columns are present. Setting sep2='' otherwise quote='auto' would "
 "quote fields containing sep2.\n"
-msgstr "当前没有列表页. 设置sep2=''否则quote='auto'会自动为所有包含sep2的字段加上引号.\n"
+msgstr ""
+"当前没有列表页. 设置sep2=''否则quote='auto'会自动为所有包含sep2的字段加上引"
+"号.\n"
 
 #: fwriteR.c:266
 #, c-format
@@ -3363,17 +3360,10 @@ msgstr "sep ('%c'), sep2 ('%c') 和 dec ('%c') 必须都不相同. 列 %d 是一
 msgid "env is not an environment"
 msgstr "env不是环境"
 
-#: gsumm.c:45
-msgid "o is not an integer vector"
-msgstr "o不是整数向量"
-
-#: gsumm.c:46
-msgid "f is not an integer vector"
-msgstr "f不是一个整数向量"
-
-#: gsumm.c:47
-msgid "l is not an integer vector"
-msgstr "l 不是整数向量"
+#: gsumm.c:45 gsumm.c:46 gsumm.c:47
+#, c-format
+msgid "%s is not an integer vector"
+msgstr "%s不是整数向量"
 
 #: gsumm.c:56
 msgid "irowsArg is neither an integer vector nor NULL"
@@ -3382,7 +3372,7 @@ msgstr "irowsArg 既不是整数向量也不是 NULL"
 #: gsumm.c:58
 #, c-format
 msgid "length(f)=%d != length(l)=%d"
-msgstr ""
+msgstr "length(f)=%d != length(l)=%d"
 
 #: gsumm.c:66
 #, c-format
@@ -3434,7 +3424,7 @@ msgstr "gather 已支持 INTSXP，REALSXP 和 CPLXSXP，但不支持 '%s'"
 #: gsumm.c:336 gsumm.c:568
 #, c-format
 msgid "%.3fs\n"
-msgstr ""
+msgstr "%.3fs\n"
 
 #: gsumm.c:345
 msgid "sum is not meaningful for factors."
@@ -3445,10 +3435,11 @@ msgstr "因子的和没有意义。"
 msgid "This gsum took (narm=%s) ... "
 msgstr "gsum 占用了 (narm=%s) ..."
 
-#: gsumm.c:350 gsumm.c:606
+#: gsumm.c:350 gsumm.c:606 gsumm.c:693 gsumm.c:812 gsumm.c:955 gsumm.c:1005
+#: gsumm.c:1085 gsumm.c:1176 gsumm.c:1266 gsumm.c:1409
 #, c-format
-msgid "nrow [%d] != length(x) [%d] in gsum"
-msgstr "gsum 中 nrow [%d] != length(x) [%d]"
+msgid "nrow [%d] != length(x) [%d] in %s"
+msgstr "%3$s 中 nrow [%1$d] != length(x) [%2$d]"
 
 #: gsumm.c:404
 msgid ""
@@ -3530,11 +3521,6 @@ msgstr ""
 msgid "min is not meaningful for factors."
 msgstr "因子的最小值没有意义。"
 
-#: gsumm.c:693
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gmin"
-msgstr "gmin 中 nrow [%d] != length(x) [%d]"
-
 #: gsumm.c:717 gsumm.c:850
 msgid ""
 "No non-missing values found in at least one group. Coercing to numeric type "
@@ -3586,11 +3572,6 @@ msgstr ""
 msgid "max is not meaningful for factors."
 msgstr "因子的最大值是没有意义的"
 
-#: gsumm.c:812
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gmax"
-msgstr "gmax检测到行数[%d]不等于x的长度[%d]"
-
 #: gsumm.c:930
 msgid ""
 "No non-missing values found in at least one group. Returning '-Inf' for such "
@@ -3628,11 +3609,6 @@ msgstr ""
 msgid "median is not meaningful for factors."
 msgstr "因子的中位值没有意义。"
 
-#: gsumm.c:955
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gmedian"
-msgstr "gmedian函数检测到行数[%d]不等于x的长度[%d]"
-
 #: gsumm.c:992
 #, c-format
 msgid ""
@@ -3643,11 +3619,6 @@ msgstr ""
 "GForce函数median (gmedian)不支持类型'%s'。请使用 stats::tail(.) 或者设置 "
 "options(datatable.optimize=1) 来关掉GForce优化。"
 
-#: gsumm.c:1005
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gtail"
-msgstr "gtail函数检测到行数[%d]不等于x的长度[%d]"
-
 #: gsumm.c:1073
 #, c-format
 msgid ""
@@ -3657,11 +3628,6 @@ msgstr ""
 "GForce函数tail (gtail)不支持类型'%s'。请使用 utils::tail(.) 或者设置 "
 "options(datatable.optimize=1) 来关掉GForce优化。"
 
-#: gsumm.c:1085 gsumm.c:1176
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in ghead"
-msgstr "ghead函数检测到行数[%d]不等于x的长度[%d]"
-
 #: gsumm.c:1153
 #, c-format
 msgid ""
@@ -3675,20 +3641,20 @@ msgstr ""
 msgid ""
 "Internal error, gtail is only implemented for n=1. This should have been "
 "caught before. please report to data.table issue tracker."
-msgstr ""
+msgstr "内部错误：gtail仅能应用于n=1的情况。此错误理应已被处理。请在 data.table 的 GitHub中提交报告。"
 
 #: gsumm.c:1166
 msgid ""
 "Internal error, ghead is only implemented for n=1. This should have been "
 "caught before. please report to data.table issue tracker."
-msgstr ""
+msgstr "内部错误：ghead仅能应用于n=1的情况。此错误理应已被处理。请在 data.table 的 GitHub中提交报告。"
 
 #: gsumm.c:1172
 msgid ""
 "Internal error, `g[` (gnthvalue) is only implemented single value subsets "
 "with positive index, e.g., .SD[2]. This should have been caught before. "
 "please report to data.table issue tracker."
-msgstr ""
+msgstr "内部错误：`g[` (gnthvalue) 仅能用于采用单个正数索引求取子集，如 .SD[2]。此错误理应已被处理。请在 data.table 的 GitHub中提交报告。"
 
 #: gsumm.c:1250
 #, c-format
@@ -3696,7 +3662,7 @@ msgid ""
 "Type '%s' not supported by GForce subset `[` (gnthvalue). Either add the "
 "prefix utils::head(.) or turn off GForce optimization using "
 "options(datatable.optimize=1)"
-msgstr ""
+msgstr "GForce取子集运算符`[` (gnthvalue)尚不支持'%s'类型。。请添加前缀stats::var(.)，或使用options(datatable.optimize=1) 关闭 GForce优化"
 
 #: gsumm.c:1262
 msgid ""
@@ -3706,23 +3672,18 @@ msgid ""
 "using options(datatable.optimize=1). Alternatively, if you only need the "
 "diagonal elements, 'DT[,lapply(.SD,var),by=,.SDcols=]' is the optimized way "
 "to do this."
-msgstr ""
+msgstr "GForce var/sd 仅能应用于列，而非.SD或其他。若要求取某一列表，如.SD，所有元素的全协方差矩阵，请添加前缀stats::var(.SD)（或stats::sd(.SD)），或使用options(datatable.optimize=1) 关闭 GForce优化。另外，若仅需获得对角线元素，最佳的方式是使用'DT[,lapply(.SD,var),by=,.SDcols=]'。"
 
 #: gsumm.c:1263
 msgid "var/sd is not meaningful for factors."
-msgstr ""
-
-#: gsumm.c:1266
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gvar"
-msgstr ""
+msgstr "无法对因子类型使用 var/sd。"
 
 #: gsumm.c:1382
 #, c-format
 msgid ""
 "Type '%s' not supported by GForce var (gvar). Either add the prefix stats::"
 "var(.) or turn off GForce optimization using options(datatable.optimize=1)"
-msgstr ""
+msgstr "GForce var (gvar) 尚不支持 '%s'类型。请添加前缀stats::var(.)，或使用options(datatable.optimize=1) 关闭 GForce优化"
 
 #: gsumm.c:1384
 #, c-format
@@ -3748,11 +3709,6 @@ msgstr ""
 msgid "prod is not meaningful for factors."
 msgstr "prod对于因子是没有意义的"
 
-#: gsumm.c:1409
-#, c-format
-msgid "nrow [%d] != length(x) [%d] in gprod"
-msgstr "在gprod中，nrow [%d] != length(x) [%d]"
-
 #: gsumm.c:1411
 #, c-format
 msgid "Unable to allocate %d * %d bytes for gprod"
@@ -4340,12 +4296,12 @@ msgstr ""
 msgid ""
 "Failed to allocate working memory for %d factor levels of result column %d "
 "when reading item %d of item %d"
-msgstr ""
+msgstr "当读取第%4$d项的第%3$d个子项时，无法为第%2$d列的%1$d个因素水平分配工作内存"
 
 #: rbindlist.c:523
 #, c-format
 msgid "Column %d of item %d: %s"
-msgstr ""
+msgstr "第 %2$d 项的第 %1$d 列: %3$s"
 
 #: reorder.c:17
 #, c-format
diff --git a/src/fread.c b/src/fread.c
index bac355b913..69082c5d95 100644
--- a/src/fread.c
+++ b/src/fread.c
@@ -1155,7 +1155,7 @@ int freadMain(freadMainArgs _args) {
     if (args.skipNrow >= 0) DTPRINT(_("  skip num lines = %"PRId64"\n"), (int64_t)args.skipNrow);
     if (args.skipString) DTPRINT(_("  skip to string = <<%s>>\n"), args.skipString);
     DTPRINT(_("  show progress = %d\n"), args.showProgress);
-    DTPRINT(_("  0/1 column will be read as %s\n"), args.logical01? _("boolean") : _("integer"));
+    DTPRINT(_("  0/1 column will be read as %s\n"), args.logical01? "boolean" : "integer");
   }
 
   stripWhite = args.stripWhite;
@@ -1771,7 +1771,7 @@ int freadMain(freadMainArgs _args) {
     }
     if (verbose) {
       if (sampleLines==0) {
-        DTPRINT(_("  'header' determined to be %s because there are%s number fields in the first and only row\n"), args.header?_("true"):_("false"), args.header?_(" no"):"");
+        DTPRINT(_("  'header' determined to be %s because there are%s number fields in the first and only row\n"), args.header?"TRUE":"FALSE", args.header?_(" no"):"");
       } else {
         if (args.header)
           DTPRINT(_("  'header' determined to be true because all columns are type string and a better guess is not possible\n"));
diff --git a/src/gsumm.c b/src/gsumm.c
index e106ddc336..210b6d7bf5 100644
--- a/src/gsumm.c
+++ b/src/gsumm.c
@@ -42,9 +42,9 @@ SEXP gforce(SEXP env, SEXP jsub, SEXP o, SEXP f, SEXP l, SEXP irowsArg) {
   const bool verbose = GetVerbose();
   if (TYPEOF(env) != ENVSXP) error(_("env is not an environment"));
   // The type of jsub is pretty flexbile in R, so leave checking to eval() below.
-  if (!isInteger(o)) error(_("o is not an integer vector"));
-  if (!isInteger(f)) error(_("f is not an integer vector"));
-  if (!isInteger(l)) error(_("l is not an integer vector"));
+  if (!isInteger(o)) error(_("%s is not an integer vector"), "o");
+  if (!isInteger(f)) error(_("%s is not an integer vector"), "f");
+  if (!isInteger(l)) error(_("%s is not an integer vector"), "l");
   if (isNull(irowsArg)) {
     irows = NULL;
     irowslen = -1;
@@ -347,7 +347,7 @@ SEXP gsum(SEXP x, SEXP narmArg, SEXP warnOverflowArg)
   double started = wallclock();
   const bool verbose=GetVerbose();
   if (verbose) Rprintf(_("This gsum took (narm=%s) ... "), narm?"TRUE":"FALSE");
-  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in gsum"), nrow, n);
+  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in %s"), nrow, n, "gsum");
   bool anyNA=false;
   SEXP ans;
   switch(TYPEOF(x)) {
@@ -603,7 +603,7 @@ SEXP gmean(SEXP x, SEXP narm)
   }
   // na.rm=TRUE.  Similar to gsum, but we need to count the non-NA as well for the divisor
   const int n = (irowslen == -1) ? length(x) : irowslen;
-  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in gsum"), nrow, n);
+  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in %s"), nrow, n, "gsum");
 
   long double *s = calloc(ngrp, sizeof(long double)), *si=NULL;  // s = sum; si = sum imaginary just for complex
   if (!s) error(_("Unable to allocate %d * %d bytes for sum in gmean na.rm=TRUE"), ngrp, sizeof(long double));
@@ -690,7 +690,7 @@ SEXP gmin(SEXP x, SEXP narm)
   int n = (irowslen == -1) ? length(x) : irowslen;
   //clock_t start = clock();
   SEXP ans;
-  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in gmin"), nrow, n);
+  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in %s"), nrow, n, "gmin");
   int protecti=0;
   switch(TYPEOF(x)) {
   case LGLSXP: case INTSXP:
@@ -809,7 +809,7 @@ SEXP gmax(SEXP x, SEXP narm)
   int n = (irowslen == -1) ? length(x) : irowslen;
   //clock_t start = clock();
   SEXP ans;
-  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in gmax"), nrow, n);
+  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in %s"), nrow, n, "gmax");
 
   // TODO rework gmax in the same way as gmin and remove this *update
   char *update = (char *)R_alloc(ngrp, sizeof(char));
@@ -952,7 +952,7 @@ SEXP gmedian(SEXP x, SEXP narmArg) {
   if (inherits(x, "factor")) error(_("median is not meaningful for factors."));
   const bool isInt64 = INHERITS(x, char_integer64), narm = LOGICAL(narmArg)[0];
   int n = (irowslen == -1) ? length(x) : irowslen;
-  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in gmedian"), nrow, n);
+  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in %s"), nrow, n, "gmedian");
   SEXP ans = PROTECT(allocVector(REALSXP, ngrp));
   double *ansd = REAL(ans);
   switch(TYPEOF(x)) {
@@ -1002,7 +1002,7 @@ SEXP glast(SEXP x) {
   R_len_t i,k;
   int n = (irowslen == -1) ? length(x) : irowslen;
   SEXP ans;
-  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in gtail"), nrow, n);
+  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in %s"), nrow, n, "gtail");
   switch(TYPEOF(x)) {
   case LGLSXP: {
     const int *ix = LOGICAL(x);
@@ -1082,7 +1082,7 @@ SEXP gfirst(SEXP x) {
   R_len_t i,k;
   int n = (irowslen == -1) ? length(x) : irowslen;
   SEXP ans;
-  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in ghead"), nrow, n);
+  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in %s"), nrow, n, "ghead");
   switch(TYPEOF(x)) {
   case LGLSXP: {
     int const *ix = LOGICAL(x);
@@ -1173,7 +1173,7 @@ SEXP gnthvalue(SEXP x, SEXP valArg) {
   R_len_t i,k, val=INTEGER(valArg)[0];
   int n = (irowslen == -1) ? length(x) : irowslen;
   SEXP ans;
-  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in ghead"), nrow, n);
+  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in %s"), nrow, n, "ghead");
   switch(TYPEOF(x)) {
   case LGLSXP: {
     const int *ix = LOGICAL(x);
@@ -1263,7 +1263,7 @@ SEXP gvarsd1(SEXP x, SEXP narm, Rboolean isSD)
   if (inherits(x, "factor")) error(_("var/sd is not meaningful for factors."));
   long double m, s, v;
   R_len_t i, j, ix, thisgrpsize = 0, n = (irowslen == -1) ? length(x) : irowslen;
-  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in gvar"), nrow, n);
+  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in %s"), nrow, n, "gvar");
   SEXP sub, ans = PROTECT(allocVector(REALSXP, ngrp));
   Rboolean ans_na;
   switch(TYPEOF(x)) {
@@ -1406,7 +1406,7 @@ SEXP gprod(SEXP x, SEXP narm)
   int n = (irowslen == -1) ? length(x) : irowslen;
   //clock_t start = clock();
   SEXP ans;
-  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in gprod"), nrow, n);
+  if (nrow != n) error(_("nrow [%d] != length(x) [%d] in %s"), nrow, n, "gprod");
   long double *s = malloc(ngrp * sizeof(long double));
   if (!s) error(_("Unable to allocate %d * %d bytes for gprod"), ngrp, sizeof(long double));
   for (i=0; i<ngrp; i++) s[i] = 1.0;