"chica" is used for infant/teen girl. "muchacha" has more a teen girl meaning. Both, however, can be used when talking about a young woman. But "mujer" always means "woman" whether she's married or not. The words for women marital designation are: - "Doncella": meant virgin woman at first but lost that connotation. Lady. - "Señorita": unmarried woman. Used also for primary school teachers. Miss. - "Señora": married woman. - "Doña": for addressing elderly women or to be very polite (now unused) with married women. - "Nona": also for addressing elderly women. Commonly used for our grandmother. If you're interested, for men are: - "Señorito": when addressing to kids. - "Señor": married/unmarried man. - "Don": masculine of "Doña". - "Nono": masculine of "Nona". Edit: Argentinian slang for women is "mina" and for men "tipo".

In Colombia chica o muchacha it's the same, for ours the age is around 15 until 20 years; we use señorita too if she's a single women or joven if he's a single man it's an formal expression

i think it's kind of diferrent in each spanish speaking country. in mexico "chica" and "muchacha" are pretty much the same, both are meant to name a female from her teens to her late twenies, more or less, but both are kind of old fashioned in my country. young people in an informal context, talking with their friends for example, use "chava" or "tipa", like: "quien es esa chava?/quien es esa tipa?" meaning who is that girl? take notice the later one, "tipa", sounds more agressive like someone you are not happy to see. in a formal context you should use "señorita" for unmarried women and "señora" for married women.

En España chica y muchacha son practicamente sinónimos. ¿Hasta que edad es una mujer chica o muchacha? Depende de la edad del que habla. Una mujer de cincuenta años llamará muchacha a una de su edad mientras que una de 15 dirá que una mujer de 50 es una vieja. Y la de 50 se enfadará y dirá que la de 15 no es una joven, es una mocosa. Supongo que esto ocurre en todos los paises Las dos palabras son adecuadas para referirse a una mujer joven, que no es una niña ni una anciana.

what a question, but answer are no less interesting. first nona/nono is italian. muchacha sounds here too rural, so whe they speak that word you know where they come from. chica is most common as every film in which tehy say" hey, girls..." they translate for chica. in fact "chica" is dialectal for "small". the mexican explanation is very interesting.: "chava" sounds like criminal slang here, and if you call anyone here "tipa" you'll have serious problems with that person. it all depends on the context i supposse. And a woman is always a woman, married or not, the thing is that men, specially old ones, say "mi mujer" when they mean "my wife".