adj. & n.
--adj.
1. (usu. foll. by to, in, or in + verbal noun) serving as an instrument or means (was instrumental in finding the money).
2 (of music) performed on instruments, without singing (cf. VOCAL).
3 of, or arising from, an instrument (instrumental error).
4 Gram. of or in the instrumental.
--n.
1. a piece of music performed by instruments, not by the voice.
2 Gram. the case of nouns and pronouns (and words in grammatical agreement with them) indicating a means or instrument.
Derivatives:
instrumentalist n. instrumentality n. instrumentally adv.
Etymology: ME f. F f. med.L instrumentalis (as INSTRUMENT)