Vocabulaire : naïf, naïve, naïveté

What do the two dots in “naïf” mean in French?

The two dots in naïf are a tréma, and they are an instruction: pronounce the two vowels separately. Without it, ai would fuse into one sound and naif would come out “nèf.” With it, you get na-ïf. The same mark is what keeps maïs (corn, ma-ïs) from being read as mais (“but”), and Noël as No-ël rather than “nol.”

The whole family carries it: naïf, naïve, naïvement, la naïveté. There is no verb, so you say être naïf or avoir de la naïveté. Other everyday trémas: aïe ! (ouch), un canoë, Israël, l’ambiguïté. It sits on the second vowel — the one that has to be pronounced apart from the letter before it.