Feeling kind of proud of myself right now.
I just successfully explained the concept of "sarcasm" (in French, un sarcasme) to my 10-year-old step-son. When he said, "Oh, it's like a mensonge (a lie)", I elaborated to explain the distinction between a lie and a sarcasm (because granted, it's a bit of a fine line). With examples.
It's rare that I can explain an actual new CONCEPT to him in French (versus a mere translation of a word). I can't even help him with his homework anymore (since he was about 7 1/2) because I'm afraid I'd cause him to make mistakes.
Score one for the American step-mom today! (And I'm not being at all sarcastic about that.)