the manner in which or the efficiency with which something reacts or fulfills its intended purpose.
Linguistics. the actual use of language in real situations, which may or may not fully reflect a speaker's competence, being subject to such nonlinguistic factors as inattention, distraction, memory lapses, fatigue, or emotional state.
late a5c., "accomplishment" (of something), from perform + -ance. Meaning "a thing performed" is from 1590s; that of "action of performing a play, etc." is from 1610s; that of "a public entertainment" is from 1709. Performance art is attested from 1971.