A mask is an object normally worn on the face, typically for protection, disguise, performance, or entertainment. Masks have been used since antiquity for both ceremonial and practical purposes, as well as in the performing arts and for entertainment. They are usually worn on the face, although they may also be positioned for effect elsewhere on the wearer's body.
More generally in art history, especially sculpture, "mask" is the term for a face without a body that is not modelled in the round, but for example appears in low relief.