Synonyms for the word "mistress" are numerous, and the choice of the right term could depend on the situation and context. Some of the common synonyms for the word "mistress" include girlfriend, lover, companion, partner, concubine, paramour, courtesan, and kept woman. While these terms may present varying levels of intimacy and commitment, they all suggest someone who is in a dominant or controlling position within a romantic or sexual relationship. However, semantics can be crucial when it comes to addressing individuals with respect and dignity. Hence, it's essential to use appropriate language while referring to people, regardless of their gender, race, or identity.