noun a device that initiates and controls nuclear reactions.

noun a response to a stimulus.

verb arrived at a destination or outcome.

verb responds or behaves in a specified way.

noun a substance used in chemical reactions to detect or measure another substance.

verb formally reacquire or regain something.

verb performs an action in response.

verb behaves in response to an event.

adjective relating to a substance that undergoes reaction.

noun a type of structured response.