A hominid is any member of the biological family Hominidae (the "great apes"), including the extinct and extant humans, chimpanzees, gorillas, and orangutans. This classification has been revised several times in the last few decades. These various revisions have led to a varied use of the word "hominid": the original meaning of Hominidae referred only to the modern meaning of Hominina, i.e. only humans and their closest relatives. The meaning of the taxon changed gradually, leading to the modern meaning of "hominid," which includes all great apes.

The primatological term hominid is easily confused with a number of very similar words:

• A hominoid or ape is a member of the superfamily Hominoidea: extant members are the lesser apes (gibbons) and great apes.
• A hominid is a member of the family Hominidae: all of the great apes.
• A hominine is a member of the subfamily Homininae: gorillas, chimpanzees, humans (excludes orangutans).
• A hominin is a member of the tribe Hominini: chimpanzees and humans.
• A hominan is a member of the sub-tribe Hominina: modern humans and their extinct relatives.
• A human is a member of Homo sapiens. The word is sometimes also used to refer to any extinct member of the genus Homo or members from other hominan genera.
• A humanoid is a vaguely human-shaped entity; the term is typically used in science fiction.

Certain morphological characteristics are still used conventionally to support the idea that hominid should only denote humans and human ancestors, namely bipedalism (walking on two feet) and large brains. These points of departure between human beings and the other great apes are important, but according to genetically based taxonomic classification, are not enough to divide us into separate families. Genetics, rather than morphology, is more widely accepted as the critical standard. Many scientists, including anthropologists, use the term hominid to mean humans and their direct and near-direct bipedal ancestors.