This question already has an answer here:

I know of three ways to express this : au fait, d'ailleurs, and à propos.

What differences are there between those three? Are they interchangeable?

merged by Stéphane Gimenez Aug 11 '14 at 10:44

This question was merged with How to translate “By the way”? — Comment traduire « By the way » ? because it is an exact duplicate of that question.

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