1. (a.) Acting as an instrument; serving as a means; contributing to promote; conductive; helpful; serviceable; as, he was instrumental in conducting the business.

2. (a.) Pertaining to, made by, or prepared for, an instrument, esp. a musical instrument; as, instrumental music, distinguished from vocal music.

3. (a.) Applied to a case expressing means or agency; as, the instrumental case. This is found in Sanskrit as a separate case, but in Greek it was merged into the dative, and in Latin into the ablative. In Old English it was a separate case, but has disappeared, leaving only a few anomalous forms.

accessory adjuvant advantageous agential agentival agentive ancillary assistant assisting auxiliary beneficial catalytic concert conducive contributory dramatico-musical employable facilitating favoring forwarding fostering handy helpful helping important intermediary jazz jazzy mediating mediatorial ministerial ministering ministrant nurtural nutricial of service orchestral promoting rock serviceable serving significant subservient subsidiary supporting supportive swing symphonic syncopated useful utilitarian valuable