a word or group of words designating something, especially in a particular field, as atom in physics, quietism in theology, adze in carpentry, or district leader in politics.
2.
any word or group of words considered as a member of a construction or utterance.
early 13c., terme "limit in time, set or appointed period," from O.Fr. terme "limit of time or place" (11c.), from L. terminus "end, boundary line," related to termen "boundary, end" (see terminus). Sense of "period of time during which something happens" first recorded
c.1300, especially of a school or law court session (mid-15c.), The meaning "word or phrase used in a limited or precise sense" is first recorded late 14c., from M.L. use to render Gk. horos "boundary," employed in mathematics and logic. Meaning "completion of the period of pregnancy" is from 1844. The verb meaning "to give a particular name to" is recorded from mid-16c. Term-paper in U.S. educational sense is recorded from 1931.