What do you call a single woman in French?

Answer 1

The normal noun or adjective to describe single people is "célibataire".

It is frequent for instance to refer to a single mother as "une mère célibataire".

As a noun, it can be used either in masculine or feminine, i.e. "une célibataire".

Note that "célibataire", in addition to the common definition of being single, also has a judicial definition meaning a person who has never been married. The marital status and the fact that you live single or not are two different notions for the purpose of the census or taxation. If you have been married but you are single now, you are not "célibataire", but separated, divorced or a widow.

The adjective "libre" (free) can also be used in some contexts.

The old term "demoiselle" is not used anymore.

The terms "jeune fille" (young girl) and "jeune femme" (young woman) may tacitly imply that the person is single, but not always. A "jeune femme" can be married too, it's just less likely because of her age.

For an older woman, there is also the deprecatory term "vieille fille" (literally old girl, in reference to the fact that it was deemed abnormal in the traditional society for a woman to reach a mature age yet not be married.)