Main Entry: mis·tress

Pronunciation: \ˈmis-trəs\

Function: noun

Etymology: Middle English maistresse, from Anglo-French mestresse, feminine of mestre master — more at master

Date: 14th century

1 : a woman who has power, authority, or ownership: as a : the female head of a household b : a woman who employs or supervises servants c : a woman who is in charge of a school or other establishment d : a woman of the Scottish nobility having a status comparable to that of a master
2 a chiefly British : a female teacher or tutor b : a woman who has achieved mastery in some field
3 : something personified as female that rules, directs, or dominates <when Rome was mistress of the world>
4 a : a woman other than his wife with whom a married man has a continuing sexual relationship b archaic : sweetheart
5 a —used archaically as a title prefixed to the name of a married or unmarried woman b chiefly Southern & Midland : mrs. 1a