Elle évite le week-end avec sa belle-mère

Does “belle-mère” mean mother-in-law or stepmother?

Belle-mère covers two people English keeps apart: your partner’s mother, and your father’s new wife. The beau- / belle- prefix marks family gained rather than born into, and it runs right through the tree — beau-père, beau-frère, belle-sœur, and les beaux-parents for the in-laws as a pair. When the difference matters, French spells it out: la mère de mon mari, la femme de mon père.

There used to be a separate word for the second case, marâtre, but it picked up a heavy pejorative charge — fairy tales did it no favours — and now reads as “cruel mother,” so it is no longer usable as a neutral label. Belle-mère absorbed both jobs — and, in French as elsewhere, picked up a small industry of jokes about the mother-in-law sense.