instrumental Definition

instrumental
adj

1. Being responsible for it or an important factor in it.

Example: She was instrumental in catching the culprit
Thesaurus: helpful, useful, contributory, assisting, influential, involved; contingent, accessory; Antonym: obstructive, unhelpful.
Form: instrumental in something (often)
Form: instrumental to something
2. Said of music: performed by, or written or arranged for, musical instruments only. Compare vocal, choral.
3. Relating to or done with an instrument or tool.
4. grammar.
Belonging to or in the instrumental case.

noun

1. A piece of music performed by or written or arranged for musical instruments only, ie with no vocal part.
2. grammar.
In some languages, eg Russian:
1a. The form or case² (sense 7) of a noun, pronoun or adjective that shows primarily how or by what means an action is performed;
1b. A noun, etc in this case.

Derivative: instrumentality
noun

Derivative: instrumentally
adverb

Etymology: 14c: French.