diff --git a/runtime/syntax/awk.vim b/runtime/syntax/awk.vim
index f80a582..40491ee 100644
--- a/runtime/syntax/awk.vim
+++ b/runtime/syntax/awk.vim
@@ -1,13 +1,15 @@
 " Vim syntax file
 " Language:	awk, nawk, gawk, mawk
 " Maintainer:	Antonio Colombo <azc100@gmail.com>
-" Last Change:	2012 May 18
+" Last Change:	2014 Oct 21
 
 " AWK  ref.  is: Alfred V. Aho, Brian W. Kernighan, Peter J. Weinberger
 " The AWK Programming Language, Addison-Wesley, 1988
 
 " GAWK ref. is: Arnold D. Robbins
 " Effective AWK Programming, Third Edition, O'Reilly, 2001
+" Effective AWK Programming, Fourth Edition, O'Reilly, 2015
+" (also available with the gawk source distribution)
 
 " MAWK is a "new awk" meaning it implements AWK ref.
 " mawk conforms to the Posix 1003.2 (draft 11.3)
@@ -33,17 +35,27 @@
 syn keyword awkStatement	break continue delete exit
 syn keyword awkStatement	function getline next
 syn keyword awkStatement	print printf return
-" GAWK ref. p. 117
+" GAWK ref. Chapter 7
 syn keyword awkStatement	nextfile
-" AWK  ref. p. 42, GAWK ref. p. 142-166
-syn keyword awkFunction	atan2 close cos exp fflush int log rand sin sqrt srand
-syn keyword awkFunction	gsub index length match split sprintf sub
-syn keyword awkFunction	substr system
-" GAWK ref. p. 142-166
-syn keyword awkFunction	asort gensub mktime strftime strtonum systime
+"
+" GAWK ref. Chapter 9, Functions
+"
+" Numeric Functions
+syn keyword awkFunction	atan2 cos div exp int log rand sin sqrt srand
+" String Manipulation Functions
+syn keyword awkFunction	asort asort1 gensub gsub index length match 
+syn keyword awkFunction	patsplit split sprintf strtonum sub substr
 syn keyword awkFunction	tolower toupper
-syn keyword awkFunction	and or xor compl lshift rshift
-syn keyword awkFunction	dcgettext bindtextdomain
+" Input Output Functions
+syn keyword awkFunction	close fflush system
+" Time Functions
+syn keyword awkFunction	mktime strftime systime
+" Bit Manipulation Functions
+syn keyword awkFunction	and compl lshift or rshift xor
+" Getting Type Function
+syn keyword awkFunction	isarray
+" String-Translation Functions
+syn keyword awkFunction	bindtextdomain dcgettext dcngetext
 
 syn keyword awkConditional	if else
 syn keyword awkRepeat	while for
@@ -51,13 +63,16 @@
 syn keyword awkTodo		contained TODO
 
 syn keyword awkPatterns	BEGIN END
-" AWK  ref. p. 36
-syn keyword awkVariables	ARGC ARGV FILENAME FNR FS NF NR
-syn keyword awkVariables	OFMT OFS ORS RLENGTH RS RSTART SUBSEP
-" GAWK ref. p. 120-126
-syn keyword awkVariables	ARGIND BINMODE CONVFMT ENVIRON ERRNO
-syn keyword awkVariables	FIELDWIDTHS IGNORECASE LINT PROCINFO
-syn keyword awkVariables	RT RLENGTH TEXTDOMAIN
+
+" GAWK ref. Chapter 7
+" Built-in Variables That Control awk
+syn keyword awkVariables        BINMODE CONVFMT FIELDWIDTHS FPAT FS
+syn keyword awkVariables	IGNORECASE LINT OFMT OFS ORS PREC
+syn keyword awkVariables	ROUNDMODE RS SUBSEP TEXTDOMAIN
+" Built-in Variables That Convey Information
+syn keyword awkVariables	ARGC ARGV ARGIND ENVIRON ERRNO FILENAME
+syn keyword awkVariables	FNR NF FUNCTAB NR PROCINFO RLENGTH RSTART 
+syn keyword awkVariables	RT SYMTAB
 
 syn keyword awkRepeat	do
 
@@ -115,15 +130,15 @@
 "syn match  awkIdentifier	"\<[a-zA-Z_][a-zA-Z0-9_]*\>"
 
 " Arithmetic operators: +, and - take care of ++, and --
-"syn match   awkOperator	"+\|-\|\*\|/\|%\|="
-"syn match   awkOperator	"+=\|-=\|\*=\|/=\|%="
-"syn match   awkOperator	"^\|^="
+syn match   awkOperator	"+\|-\|\*\|/\|%\|="
+syn match   awkOperator	"+=\|-=\|\*=\|/=\|%="
+syn match   awkOperator	"^\|^="
 
 " Comparison expressions.
-"syn match   awkExpression	"==\|>=\|=>\|<=\|=<\|\!="
-"syn match   awkExpression	"\~\|\!\~"
-"syn match   awkExpression	"?\|:"
-"syn keyword awkExpression	in
+syn match   awkExpression	"==\|>=\|=>\|<=\|=<\|\!="
+syn match   awkExpression	"\~\|\!\~"
+syn match   awkExpression	"?\|:"
+syn keyword awkExpression	in
 
 " Boolean Logic (OR, AND, NOT)
 "syn match  awkBoolLogic	"||\|&&\|\!"
@@ -187,8 +202,8 @@
   HiLink awkFloat		Float
 
   HiLink awkFileIO		Special
-  "HiLink awkOperator		Special
-  "HiLink awkExpression		Special
+  HiLink awkOperator		Special
+  HiLink awkExpression		Special
   HiLink awkBoolLogic		Special
 
   HiLink awkPatterns		Special