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 a4a04fd5ff..e26f29a6f4 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 8fc0afd67e..844c98f588 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/po/R-zh_CN.po b/po/R-zh_CN.po
index e5d0c51a40..643348d63e 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: 2019-10-21 16:15\n"
+"POT-Creation-Date: 2019-12-22 23:59\n"
 "PO-Revision-Date: 2019-11-16 18:37+0800\n"
 "Last-Translator: Xianying Tan <shrektan@126.com>\n"
 "Language-Team: Mandarin\n"
@@ -2243,32 +2243,32 @@ msgid ""
 msgstr "因子列和 ignore.row.order 都不能与非 0 的容差（tolerance）参数同时使用"
 
 msgid "Internal error: factor type mismatch should have been caught earlier"
-msgstr "内部错误：请提前排查不匹配的因子类型"
+msgstr "内部错误：此时不匹配的因子类型应已被发现"
 
 msgid "argument 'fill' ignored, only make sense for type='const'"
-msgstr "参数 'fill' 被忽略，仅对 'const' 类型有意义"
+msgstr "参数 'fill' 将被忽略，因其仅当 type='const'时有意义"
 
 msgid "order.col='"
-msgstr "按列排序 = '"
+msgstr "order.col='"
 
 msgid "' not a column name of info"
-msgstr "' 不是如下信息的列名："
+msgstr "' 并非info的一个列名"
 
 msgid "data.table package is loaded. Unload or start a fresh R session."
-msgstr ""
-"data.table 包加载完毕，并将一直可用，直到其被卸载或启用一个新的 R 会话为止。"
+msgstr "data.table 包已被加载。请将其卸载或启动一个新的 R 会话。"
 
 msgid ""
 "script must end with '.Rraw'. If a file ending '.Rraw.bz2' exists, that will "
 "be found and used."
 msgstr ""
-"脚本必须以 '.Rraw' 结尾。如果以 'Rraw.bz2' 结尾的文件存在，也将被发现和使用。"
+"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 ""
+msgstr "均不存在于文件夹"
 
 msgid "Failed after test"
 msgstr ""
@@ -2277,62 +2277,62 @@ msgid "before the next test() call in"
 msgstr ""
 
 msgid "out of"
-msgstr ""
+msgstr "总数为"
 
 msgid ". Search"
-msgstr ""
+msgstr ". 搜索"
 
 msgid "for test number"
-msgstr ""
+msgstr "以获得测试编号"
 
 msgid "Timings count mismatch:"
-msgstr ""
+msgstr "计时不一致:"
 
 msgid "vs"
-msgstr ""
+msgstr "vs"
 
 msgid "Test"
-msgstr ""
+msgstr "测试"
 
 msgid ""
 "is invalid: when error= is provided it does not make sense to pass y as well"
-msgstr ""
+msgstr "无效：当使用了error=，不应再输入y"
 
 msgid "Use started.at=proc.time() not Sys.time() (POSIXt and slow)"
-msgstr ""
+msgstr "使用started.at=proc.time()而非Sys.time() (返回POSIXt类型，处理较慢)"
 
 msgid "make.names='"
-msgstr ""
+msgstr "make.names='"
 
 msgid "' not found in names of input"
-msgstr ""
+msgstr "'不存在于输入的名字里"
 
 msgid "make.names="
-msgstr ""
+msgstr "make.names="
 
 msgid "is out of range [1,ncol="
-msgstr ""
+msgstr "不在以下区间[1,ncol="
 
 msgid "'names' must be TRUE/FALSE or a character vector."
-msgstr ""
+msgstr "'names'必须为TRUE/FALSE，或一个字符（character）向量。"
 
 msgid "'keep' should contain integer values between"
-msgstr ""
+msgstr "'keep'所含整数值应在区间"
 
 msgid "length(names) (="
-msgstr ""
+msgstr "length(names) (="
 
 msgid ") is not equal to length("
-msgstr ""
+msgstr ") 并不等于(="
 
 msgid ") (="
-msgstr ""
+msgstr ") (="
 
 msgid ")."
-msgstr ""
+msgstr ")."
 
 msgid "l not type list"
-msgstr ""
+msgstr "l并非列表（list）类型"
 
 msgid "Argument 'nan' must be length 1"
 msgstr ""
@@ -2341,7 +2341,7 @@ msgid "Argument 'nan' must be NA or NaN"
 msgstr ""
 
 msgid "x not boolean"
-msgstr ""
+msgstr "x并非布尔值"
 
 msgid ""
 "Some columns are type 'integer64' but package bit64 is not installed. Those "
@@ -2349,29 +2349,45 @@ msgid ""
 "to reload the data. Simply install.packages('bit64') to obtain the integer64 "
 "print method and print the data again."
 msgstr ""
+"有些列的类型是64 位整数类型（'integer64')但bit64包并没有安装。这些列会被显示"
+"成看起来有些奇怪的浮点型数据。然而并不需要重新载入这些数据，只需运行 install."
+"packages('bit64') 来获取显示integer64类型的打印方法，再重新打印该数据即可。"
 
 msgid "Pattern"
-msgstr ""
+msgstr "Pattern"
 
 msgid "not found: ["
-msgstr ""
+msgstr "未找到: ["
 
 msgid ""
 "Input xts object should not have 'index' column because it would result in "
 "duplicate column names. Rename 'index' column in xts or use `keep."
 "rownames=FALSE` and add index manually as another column."
 msgstr ""
+"输入的xts对象不能含有'index'列，因这会导致出现重复的列名。请尝试重新命名xts中"
+"的'index'列或者使用`keep.rownames=FALSE`并手动添加index为另外的列"
 
 msgid ""
 "data.table must have a time based column in first position, use "
 "`setcolorder` function to change the order, or see ?timeBased for supported "
 "types"
 msgstr ""
+"data.table的首列必须为一个以时间为基础的列，请使用`setcolorder`方程来改变它的"
+"顺序，或者通过?timeBased来查看支持的类型"
 
 msgid "Following columns are not numeric and will be omitted:"
-msgstr ""
+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 ". ["
diff --git a/po/zh_CN.po b/po/zh_CN.po
index b53759e053..b478dcdba0 100644
--- a/po/zh_CN.po
+++ b/po/zh_CN.po
@@ -4578,117 +4578,119 @@ msgstr "输入到 'uniqlengths' 的参数 'n' 必须是长度为 1 的整数向
 
 #: uniqlist.c:167
 msgid "cols must be an integer vector with length >= 1"
-msgstr ""
+msgstr "cols必须是一个长度大于等于1的整数向量"
 
 #: uniqlist.c:171
 #, c-format
 msgid "Item %d of cols is %d which is outside range of l [1,length(l)=%d]"
-msgstr ""
+msgstr "列的%d项是%d，它超出l的所在区间[1,length(l)=%d]"
 
 #: uniqlist.c:174
 #, c-format
 msgid ""
 "All elements to input list must be of same length. Element [%d] has length "
 "%<PRIu64> != length of first element = %<PRIu64>."
-msgstr ""
+msgstr "列表的所有元素必须是同样的长度。元素[%d]的长度%<PRIu64>不等于"
+"第一个元素的长度%<PRIu64>"
 
 #: uniqlist.c:255
 msgid "Internal error: nestedid was not passed a list length 1 or more"
-msgstr ""
+msgstr "内部错误：nestedid并不是一个长度大于或者等于1的列表"
 
 #: uniqlist.c:262
 #, c-format
 msgid "Internal error: nrows[%d]>0 but ngrps==0"
-msgstr ""
+msgstr "内部错误：nrows[%d]>0但是but ngrps==0"
 
 #: uniqlist.c:264
 msgid "cols must be an integer vector of positive length"
-msgstr ""
+msgstr "cols必须是一个长度大于零的整数向量"
 
 #: uniqlist.c:349
 msgid "x is not a logical vector"
-msgstr ""
+msgstr "x不是一个逻辑向量"
 
 #: utils.c:73
 #, c-format
 msgid "Unsupported type '%s' passed to allNA()"
-msgstr ""
+msgstr "allNA() 不支持'%s'类型"
 
 #: utils.c:92
 msgid "'x' argument must be data.table compatible"
-msgstr ""
+msgstr "'x' 必须为data.table支持的类型"
 
 #: utils.c:94
 msgid "'check_dups' argument must be TRUE or FALSE"
-msgstr ""
+msgstr "参数'check_dups'必须为TRUE或者是FALSE"
 
 #: utils.c:110
 msgid ""
 "argument specifying columns is type 'double' and one or more items in it are "
 "not whole integers"
-msgstr ""
+msgstr "指定列的参数是一个双精度类型而其中至少有一个元素不是整数"
 
 #: utils.c:116
 #, c-format
 msgid "argument specifying columns specify non existing column(s): cols[%d]=%d"
-msgstr ""
+msgstr "指定列的参数指定了不存在的列: cols[%d]=%d"
 
 #: utils.c:121
 msgid "'x' argument data.table has no names"
-msgstr ""
+msgstr "data.table的参数x并没有名字"
 
 #: utils.c:126
 #, c-format
 msgid ""
 "argument specifying columns specify non existing column(s): cols[%d]='%s'"
-msgstr ""
+msgstr "指定列的参数指定了不存在的列: cols[%d]='%s'"
 
 #: utils.c:129
 msgid "argument specifying columns must be character or numeric"
-msgstr ""
+msgstr "指定列的参数必须是字符或者是数值"
 
 #: utils.c:132
 msgid "argument specifying columns specify duplicated column(s)"
-msgstr ""
+msgstr "指定列的参数指定了重复的列"
 
 #: utils.c:138
 #, c-format
 msgid "%s: fill argument must be length 1"
-msgstr ""
+msgstr "%s：fill参数的长度必须为1"
 
 #: utils.c:171
 #, c-format
 msgid "%s: fill argument must be numeric"
-msgstr ""
+msgstr "%s：fill参数必须为数值类型"
 
 #: utils.c:273
 #, c-format
 msgid "Internal error: unsupported type '%s' passed to copyAsPlain()"
-msgstr ""
+msgstr "内部错误：copyAsPlain()不支持类型为'%s'的参数"
 
 #: utils.c:277
 #, c-format
 msgid ""
 "Internal error: type '%s' passed to copyAsPlain() but it seems "
 "copyMostAttrib() retains ALTREP attributes"
-msgstr ""
+msgstr "内部错误：copyAsPlain()中参数为'%s'类型，但"
+"copyMostAttrib() 保留了ALTREP属性"
 
 #: utils.c:312
 #, c-format
 msgid "Found and copied %d column%s with a shared memory address\n"
-msgstr ""
+msgstr "发现并拷贝了具有相同的内存地址的%d列%s\n"
 
 #: vecseq.c:13
 msgid "x must be an integer vector"
-msgstr ""
+msgstr "x必须为一个整数向量"
 
 #: vecseq.c:14
 msgid "len must be an integer vector"
-msgstr ""
+msgstr "len必须为一个整数向量"
 
 #: vecseq.c:15
 msgid "x and len must be the same length"
-msgstr ""
+msgstr "x和len必须长度一致"
 
 #: vecseq.c:21
 msgid ""
@@ -4699,14 +4701,20 @@ msgid ""
 "Otherwise, please search for this error message in the FAQ, Wiki, Stack "
 "Overflow and data.table issue tracker for advice."
 msgstr ""
+"连接后将生成超过2^31行（已达内部的vecseq的物理"
+"极限）。这很可能是一个错误的连接操作。请检查i中是否存在重复的键值（key values），"
+"导致x中对应的组反复连接。若确定重复的连接可授受，可尝试 by=.EACHI "
+"以使j中的语句仅在每个 i 中对应的组运行以避免大量的内存分配。"
+"否则，请在常见问题（FAQ）、维基（Wiki）、Stack "
+"Overflow 和 data.table GitHub Issue中寻求帮助。"
 
 #: vecseq.c:25
 msgid "clamp must be a double vector length 1"
-msgstr ""
+msgstr "clamp 必须为一个长度为1的双精度向量"
 
 #: vecseq.c:27
 msgid "clamp must be positive"
-msgstr ""
+msgstr "clamp必须为正数"
 
 #: vecseq.c:28
 #, c-format
@@ -4717,39 +4725,46 @@ msgid ""
 "large allocation. If you are sure you wish to proceed, rerun with allow."
 "cartesian=TRUE. Otherwise, please search for this error message in the FAQ, "
 "Wiki, Stack Overflow and data.table issue tracker for advice."
-msgstr ""
+msgstr "连接后生成%d行；多于%d = nrow(x)+nrow(i)。请检查"
+"i中是否存在重复的键值（key values），导致x中对应的组反复连接。"
+"若确定重复的连接可授受，可尝试 by=.EACHI 以使j中的语句仅在每个 i 中对应的组运行"
+"以避免大量的内存分配。如果确认要继续，请设置"
+"cartesian=TRUE 并重新运行。否则，请在常见问题（FAQ）、"
+"维基（Wiki）、Stack Overflow 和 data.table GitHub Issue中寻求帮助。"
 
 #: wrappers.c:11
 msgid "Attribute name must be a character vector of length 1"
-msgstr ""
+msgstr "属性的名字必须为一个长度为1的字符向量"
 
 #: wrappers.c:16
 msgid ""
 "Internal structure doesn't seem to be a list. Can't set class to be 'data."
 "table' or 'data.frame'. Use 'as.data.table()' or 'as.data.frame()' methods "
 "instead."
-msgstr ""
+msgstr "内部结构并不非一个列表。无法将目标的类型设置为一个data.table"
+"或data.frame。请使用'as.data.table()' 或 'as.data.frame()'."
 
 #: wrappers.c:66
 msgid "First argument to setlistelt must be a list()"
-msgstr ""
+msgstr "setlistelt的第一个参数必须是一个列表"
 
 #: wrappers.c:67
 msgid "Second argument to setlistelt must a length 1 integer vector"
-msgstr ""
+msgstr "setlistelt的第二个参数必须为一个长度为1的整数向量"
 
 #: wrappers.c:69
 #, c-format
 msgid "i (%d) is outside the range of items [1,%d]"
-msgstr ""
+msgstr "i (%d)超出了[1,%d]的范围"
 
 #: wrappers.c:91
 msgid "x isn't a VECSXP"
-msgstr ""
+msgstr "x并非一个VECSXP"
 
 #: wrappers.c:106
 #, c-format
 msgid ""
 "dim.data.table expects a data.table as input (which is a list), but seems to "
 "be of type %s"
-msgstr ""
+msgstr "dim.data.table的参数必须为一个data.table（实质为一个列表），但输入参数"
+"为%s类型"