Ms. is a common English honorific used to describe women without saying if they are married or unmarried. Ms. was invented to replace Mrs. (only for married women) and Miss (for unmarried women). American feminists supported the idea of using "Ms." Now, most American women use "Ms.". The word and idea of "Ms." has a very complicated and complex history.
The honorific "Ms." goes back to at least the 1760s. But, it was more "officially" proposed by a writer in 1901. This writer proposed "Ms." to avoid accidentally calling a woman a wrong name. This proposal was also the first marriage-neutral proposal. "Ms." was accepted as an honorific by the New York Times in 1986. Later, during a radio interview at the New York Radio Station, Sheila Michaels spoke out for the honorific "Ms." to be a title. Eventually, "Ms." became official.