1911 Encyclopædia Britannica/Mistress

MISTRESS (adapted from O. Fr. maistresse, mod. maîtresse, the feminine of maistre, maître, master), a woman who has authority, particularly over a household. As a form of address or term of courtesy the word is used in the same sense as “madam.” It was formerly used indifferently of married or unmarried women, but now, written in the abbreviated form “Mrs” (pronounced “missis”), it is practically confined to married women and prefixed to the surname; it is frequently retained, however, in the case of spinster cooks or housekeepers, as a title of dignity; as the female equivalent of “master” the word is used in other senses by analogy, e.g. of Rome as “the mistress of the world,” Venice “the mistress of the Adriatic,” &c. From the common use of “master” as a teacher, “mistress” is similarly used. The old usage of the word for a lady-love or sweetheart has degenerated into that of paramour. “Miss” a shortened form of “mistress,” is the term of address for a girl or unmarried woman; it is prefixed to the surname in the case of the eldest or only daughter of a family, and to the Christian names in the case of the younger daughters.