- Acting as an instrument; serving as a means; contributing to promote; conductive; helpful; serviceable; essential or central .
- ( music ) Pertaining to, made by, or prepared for, an instrument, especially a musical instrument .
- ( grammar ) Applied to a case expressing means or agency, generally indicated in English by by or with with the objective .
From Middle English, from Medieval Latin instrumentalis, from instruere ( "to build into, set up, construct, furnish," hence "to train" ), from in- ( "on" ) + struere ( "to put together, arrange, pile up, build, construct" ), from Proto-Indo-European *strew- ( “to spread, to strew” ) .
Explanation of instrumental by Wordnet Dictionary