Ms. is actually the title that was promoted as a less-sexist alternative to Miss/Mrs. which, like Mr., does not depend on marital status.
Miss is the one specific to unmarried women.
Miss is the one specific to unmarried women.
I got this impression from my father. When I was little I would help stamp and address sales mailers he would send out, and he always used Ms. When I asked him, he said start with Ms. and let them correct you if they want something different. But, some divorced women get angry at being referred to as Mrs.
I also never said we should or shouldn't use the terms. I don't have an opinion on that and it's not a debate or argument I'm going to waste my time on. I was simply explaining how they are conventionally used. This kind of thing was taught in schools as recently as 20 years ago as part of explanations on how to write and format letters.
Edit:
It seems using it until the age of 12 is a convention in the US. Using it until 18 is the convention in the UK. Another argument for why software shouldn't make decisions using terms that can mean different things to different people :)
Not anymore, that is. It used to be an abbreviation for two appellations, one of which was associated with an unmarried gentleman. It's rarely used outside of the British Commonwealth, anymore. Except on Fresh Prince, of course.