Into every Word file, a few squiggles must fall.
In the 2019 release that is a snapshot of Word 365, the grammar and spelling tools are grouped together in a feature Microsoft has called the Editor. On screen, Word flags errors by underlining them. The underlining it uses mean the following:
- red squiggle = misspelled
- blue dots = formatting error
- blue double straight = word choice or grammar error
The flagging of homonyms has improved, as you can see in the left-hand figure, but Word still misses a lot of grammar errors and some of the formatting errors — even when it has flagged those exact errors elsewhere. The errors shown in the screen grabs below are particularly bad, but Word even misses errors they used as illustrations in Word’s own help files.
Word flagged the yellow spelling and grammar errors but missed all the blue ones. 
With all grammar options turned off, Word still flags the homonym.
Turning On Grammar & Spelling Display
- On a Mac, go to Word > Preferences > Spelling & Grammar.
- Windows users, click Options on the File menu, then select Proofing. In the area headed “When correcting spelling and grammar in Word,” click the Settings… button.
Turning Off Grammar & Spelling Display
You can turn off grammar checking, and you can deselect a lot of the checks, but even if you turn off the display of spelling errors, homonyms will still be flagged. (Right figure, top.)
While many editors turn off the grammar checker because Word’s advice is misguided more often than not, the blue “wrong word” checker cannot be turned off.
To get rid of the flags, select “Check Document” or “Recheck Document” in the spelling & grammar settings after deselecting “Mark grammar errors as you type” and “Check grammar with spelling.”
