Software that analyzes the grammar of a sentence. It can check for and highlight incomplete sentences, awkward phrases, wordiness and poor grammar.
A Grammar Error
This screen shot was excerpted from the grammar checker in the Corel WordPerfect office suite. It has highlighted the words "keys is" in the sentence because it is grammatically incorrect. Note the explanation at the bottom about subject-verb agreement. (Image courtesy of Corel Corporation, www.corel.com)