Words that are not the same but get interchanged

How about ‘quits’ as in ‘Let’s call it quits.’ ? I used to think this meant ‘Let’s quit (stop) doing something.’

A Frenchman asked me to proofread his English letter claiming that he was owed a spare part: “To be quits we need you to send a G6546 circuit board.” I said this didn’t sound like English and he showed me an English dictionary! Was I wrong? Is this a familiar usage?

I’ve heard it (esp. the phrase “call it quits”). The dictionary says the adjective “quits” = on even terms, especially because a debt or score has been settled; freed from a liability or debt – has been English since the late 15th century.

So your example is “quits” versus the verb to quit?

Ones that annoy/amuse me;

Than/then (seems to be quite common on message boards for some reason)
Enormousness/enormity (I think people use ‘enormity’ because ‘enormousness’ sounds clunky, but enormity means something completely different)
pacific/specific (this one is always good for a laugh)

Immanent vs imminent?

“Moot court” in law school is an exercise where students debate an unresolved legal problem where the evidence is considered in equilibrium, and it will be the quality of the student’s arguments that push the point one way or another. They are real situations that were made moot before they were settled for one reason or another.

This is a great example.

Lay people somehow picked up the word “moot” from legalese as meaning “something no longer worth debating,” and got the wrong idea about it, so often use it to mean something settled, as opposed to something that either can’t be, or no longer needs to be settled.

Thank you for articulating so well why this fight must be fought.

Unfortunately, this error (“comprised of” to mean “composed of”) has become so common that it is now generally regarded as standard.