A computer-implemented grammar checker for French language text corrects negation errors (missing particle "ne/n'") in French language text. A parser generates a syntax record of a verbal phrase of the text. The syntax record includes records of words in the verbal phrase, lexicon information for the words, and syntax attributes for the words. The grammar checker searches the syntax record for a missing particle "ne/n'". If the particle "ne/n'" is not found, the grammar checker calculates a syntactically correct insertion point for the particle "ne/n'". The grammar checker displays to the user a rewrite of a correct form of the particle "ne/n'" at the insertion point.