reagent

(rē-ā′jĕnt )

To hear audio pronunciation of this topic, purchase a subscription or log in.

[L. reagere, to react]

1. A substance involved in a chemical reaction.
2. A substance used to detect the presence or amount of another substance.
3. A subject of a psychological experiment, esp. one reacting to a stimulus.

There's more to see -- the rest of this topic is available only to subscribers.