simian

Simian is an adjective and noun used in biological contexts to refer to members of the clade Simiiformes, the group commonly called simians, which includes the higher primates such as monkeys and apes. The term derives from Latin simia, meaning ape or monkey. In everyday usage, simian typically denotes non-human primates, though some scientific writings use it in a broader taxonomic sense.

Taxonomically, simians form a major lineage within the suborder Haplorhini. Within Simiiformes are the two parvorders: Platyrrhini (New World monkeys) and Catarrhini (Old World monkeys and apes). Catarrhini further divides into Cercopithecoidea (Old World monkeys) and Hominoidea (apes and humans). In modern classifications, humans are placed within Hominoidea; thus they are both anthropoids and simians, though the term simian is more commonly applied to non-human primates in ordinary usage.

There are hundreds of living simian species, ranging from diminutive New World monkeys to the larger apes. Simians exhibit a wide range of adaptations in dentition, locomotion, and social systems. Common distinguishing features of simians include a relatively large brain and forward-facing eyes with stereoscopic vision, though traits vary significantly among groups.

In medicine and virology, the term simian appears as a prefix or descriptor for agents associated with non-human primates, such as simian immunodeficiency virus (SIV) and simian virus 40 (SV40). These usages reflect the primate origin of the pathogens or viruses studied.