Mistress is the feminine form of the English word "master" (master + -ess) and may refer to: Romance and relationships. Mistress (lover), a female lover of a married man. Royal mistress. Maîtresse-en-titre, official mistress of a French king. Title or form of address. Mistress (form of address) Mistress (college), a female college head. Mistress of the Robes of the UK Royal Household. Female equivalent of schoolmaster. In ancient religions. Despoina, a Greek goddess referred to as "the mistress" Potnia ("mistress lady"), a title for a Greek goddess. In arts and entertainment.
https://en.wikipedia.org/wiki/Mistress