One; having or consisting of one.
Latin unus, one.
Some examples taken from Latin include unicorn (Latin cornu, horn); unify (Latin unificare, make into a whole); uniform (Latin uniformis); universe (Latin universus, combined into one, whole); and university (Latin universitas, the whole, in late Latin referring to a society or guild).
The form is widely used: unisex refers to something, especially clothing or hairstyles, designed to be suitable for both sexes; a unipod is a one-legged support for a camera; a unitard is a one-piece garment, a version of a leotard; something unidirectional moves or operates in a single direction; an action that is unilateral is performed by only one party in a situation, so is not mutually agreed; in chemistry, something unimolecular consists of or involves a single molecule.
See also mono‑.