Reagent

[rɪ'eɪdʒ(ə)nt] or [rɪ'edʒənt]

(noun.) a chemical agent for use in chemical reactions.

Edited by Colin--From WordNet

(n.) A substance capable of producing with another a reaction, especially when employed to detect the presence of other bodies; a test.

Checker: Seymour

n. (Chem.) Test.

Typed by Felix

n. a substance that reacts on and detects the presence of other bodies: a test: one who exerts reflex influence.—n. Reā′gency.

Typed by Doreen