If someone is complicit, they’re guilty of helping someone commit a crime or misdeed. If they’re complacent, they're guilty of letting something happen even if they have the power to intervene or stop it. A complaisant person, on the other hand, is only guilty of one thing: being a people pleaser.
Complicit means acting as an accomplice to some wrongdoing — you’re complicit in your brother’s truancy if you don’t tell your parents that he wasn’t on the school bus with you. In fact, the word’s oldest etymological relative in English is the now-obsolete complice, "accomplice to a crime," from the Latin complicare, "to fold together." You may not be the one who committed the crime, but when you’re complicit, you are folded or tangled together with the criminal and hold some responsibility:
Indeed, virtually every element of society was complicit in the murderous system. (Killers of the Flower Moon)
"It’s pretty evident to me there was very, very significant fraud and that a number of parties had been complicit." (BusinessWeek)
Complacent comes from a Latin root meaning "very pleasing," which was also its original definition. The word evolved in the 18th century, eventually describing someone who is very pleasing to themselves, but much less pleasing to other people. A complacent person is so smug and confident about the way things are in their own sphere that they tend to lose track of the realities existing outside themselves. And because of this aspect, a complacent person may witness something but not do anything about it, even if they should. This is where confusion often arises with a complicit person — one who's actually doing something wrong. Check out these examples and see if you get the smug vibe or the careless, indifferent one:
Perhaps it can be said she had become too comfortable, too complacent in a neighborhood known for violent crime. (Time)
Staff members were complacent about Saito's escape risk, state Health Director Bruce Anderson said. (Fox News)
She was extravagant with her pity, and complacent in her snug world. (Go Set a Watchman)
"I have worked hard for this. But this is just starting. I am not complacent. I want to accomplish more." (The Washington Times)
A complaisant person is the best of this bunch, because they try to make other people happy. But it's sometimes used in a negative or condescending way to imply that someone is too willing or easily persuaded to do something. Like its homophone complacent, this word derives from the Latin complacere, "be very pleasing." Here are some examples in the wild:
Ida was not in a very complaisant mood, and she glanced at him coldly. (The Gold Trail)
She is restless, irritable, out of sorts, censorious, complaining at home; animated, gracious, affable, complaisant abroad. (The Five Great Philosophies of Life)
His subjects had already begun to murmur; the early parliaments of his reign had been passive and complaisant; but by 1523 the Commons had been goaded into resistance. (Encyclopaedia Britannica)
If you assume you’ll ace the test without having studied, that makes you complacent. But if you always aim to be pleasant, you’re complaisant. Find yourself involved in something illicit? Now you’re complicit.