I love latin (and greek) terms used in English. I would love to use it as a matter of routine, but I know I would harshly misuse it.
The only term I can use comfortably is pro bono... thanks to all the Grisham novels i devour.
The term I misused for the longest term, and in this I find myself in the company of a great many, is ad hoc. It means: for this purpose. However, it's used often to convey just the opposite meaning, for no particular purpose.
Here is a term that is so nice on the ear, but so difficult to use: Non sequitur (something that does not follow).
A few terms are easier to inject into your language -- that bona fide idiot who pissed you off on the road?
Persona non grata, too... not that I am one in any place or home. I think...
Here's a new one I read and really liked, and hope desperately that I would be able to use somewhere outside of this post:
Ceteris Paribus: means "other things being equal."
Then there are some that sound suspiciously like Madras pettai slang:
Mutatis mutandis (the necessary things have been changed).
Pari Passu (at an equal pace).
The really CUTE ones, which we wish had a sassy enough English equivalent.
Reductio ad absurdum stands for "reduction to absurdity."
Sui generis: "of one's own kind" or "peculiar". I would rather be Sui generis than peculiar, any day.
And RIP apparently doesn’t translate literally to Rest In Peace, but Requiescat in Pace which means "let him rest in peace."
I know that if ever I decide to study law -- and I do toy with that idea often -- one of the reasons would be all the latin lingo I will learn, and learn to use with ease. My father for instance, can turn a mundane conversation (which could well be about an ailing pet cat) into a language puzzle, dotting it with latin phrases, ad infinitum.
ps: Amavi = fall in love with