What is Grammar Check?
By default, Microsoft Word checks grammar as well as spelling. Grammatical errors are underlined with a green squiggly line. A grammar check will run when you perform a spell check.
To correct grammar, right-click on the underlined words and choose alternative phrasing. Keep in mind that the grammar check is only 75%-80% accurate.
If you don't want Microsoft Word to run grammar checks, when you run a spell check, uncheck the Check Grammar box in the Spelling and Grammar window.