What is the meaning of the abbreviation 'Ms.'?

Ms, like Mrs and Miss, is a contraction of the honorific "Mistress", which is the feminine of "Mister" or "Master". However, unlike Miss and Mrs., it does not presume the addressee's marital status. Ms. originated in the United States and was popularized in the 1970s. It is now the default form of address for business correspondence with a woman.