An earlier grammar checking program for DOS, Windows, Macintosh and Unix that was developed by Reference Software and acquired by WordPerfect Corporation in 1993. Novell later acquired WordPerfect, which it then sold to Corel. U.S. government versions checked for usage according to the Government Printing Office and other military and civilian guides. The functionality of Grammatik remained in Corel's WordPerfect office suite. See grammar checker.