Deer (singular and plural) are the ruminant mammals forming the family Cervidae. Species in the family include the white-tailed deer, mule deer (such as the black-tailed deer), elk, moose, red deer, reindeer (caribou), fallow deer, roe deer, pudú and chital. Male deer of all species (except the Chinese water deer) and female reindeer grow and shed new antlers each year. In this they differ from permanently horned animals, such as antelope, which are in the same order as deer and may bear a superficial resemblance to them.
The musk deer of Asia and water chevrotain (or mouse deer) of tropical African and Asian forests are not usually regarded as true deer and form their own families: Moschidae and Tragulidae, respectively.