Complement vs. Compliment (and Other Pairs Spellcheck Won't Catch)

Some misspellings get flagged instantly by any spellchecker. A different, sneakier category never gets flagged at all, because both spellings are correctly spelled real words, just the wrong one for the sentence. These pairs need you to actually know the difference, since no red underline is coming to save you.

Complement vs. compliment

A complement is something that completes or enhances something else: "the wine was a good complement to the meal." A compliment is a nice thing someone says about you: "she gave me a compliment on the presentation." One tiny vowel apart, and yet they don't share any meaning at all. A useful memory trick: complEment completEs something; complIment is nIce to hear.

Principal vs. principle

A principal is either the head of a school or, in a slightly different sense, the main or most important thing in a situation: "the principal reason for the delay." A principle is a fundamental rule or belief: "she refused on principle." The classic trick here: the school princiPAL is your PAL; a princiPLE is a ruLE.

Why spellcheck genuinely can't save you

Spellcheckers flag strings of letters that don't form a real word. They generally don't flag a real word used in the wrong sense, which is exactly the failure mode both of these pairs create. "He gave me a nice complement" will sail through spellcheck without a single flag, and the sentence will still be wrong.

What actually fixes it

Memory tricks like the ones above help, but the distinction only really sticks once you've deliberately used both words correctly a handful of times, which is a different kind of practice than proofreading alone provides. Our guide for writers covers more pairs like this that spellcheck quietly lets through.

Confident you'd catch both of these in your own writing without a second glance? A quiz is a fairer test than assuming so.