One who responds, or gives responses.

something said or written as an answer to something

state of being dependable or reliable

having the duty of dealing with something; being the cause or creator of something; behaving in a mature and reasonable manner

(zoology) An animal's response to a stimulus in which the animal moves in a way that allows it to better evaluate the nature of the stimulus. It can then better respond to danger through "fight or flight".

(neurophysiology) The outcome carried out by the motor effector as a result of the reflex arc.

The response of the immune system to an allergen

plural of social responsibility

(biology, medicine) The period of time between the application of a stimulus and the associated response from a cell or tissue

plural of response time