Belle-mère vs. marâtre
In French, the words 'belle-mère' and 'marâtre' both translate to 'stepmother', but they carry different connotations and usages.
Belle-mère
The word 'belle-mère' is a neutral or respectful term that refers to one's stepmother or mother-in-law. The literal translation is 'beautiful mother'.
Ma belle-mère vient dîner ce soir.
(My stepmother is coming for dinner tonight.)
Je m'entends très bien avec ma belle-mère.
(I get along very well with my stepmother.)
Sa belle-mère l'a beaucoup aidé durant son mariage.
(His mother-in-law helped him a lot during his marriage.)
Marâtre
'Marâtre' is a pejorative term that implies a wicked or cruel stepmother, evoking the stereotype often found in fairy tales and negative stories.
Dans ce conte, la princesse est maltraitée par sa marâtre.
(In this tale, the princess is mistreated by her wicked stepmother.)
Les enfants redoutaient les punitions de leur marâtre.
(The children dreaded the punishments from their evil stepmother.)
Elle parle de sa belle-mère comme si c'était une marâtre.
(She talks about her stepmother as if she were a wicked stepmother.)
Summary
In summary, 'belle-mère' is used in a neutral or affectionate context to refer to a stepmother or mother-in-law, whereas 'marâtre' carries negative connotations, often describing a cruel and unkind stepmother like those depicted in fairy tales.