MISTRESS (adapted from O. Fr. maistresse, mod. mattresse, the feminine of maistre, matlre, 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," etc. From the common use of " master " as a teacher, " mistress " is similarly used. The old usage of the word for a ladylove 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.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)