The reaction to a stimulus is called

Stimulus:

1. All living things react to changes in their environment. Stimuli are changes in the environment to which living organisms respond.
2. External stimuli such as heat, light, touch, sound, smell, taste, water, and chemicals cause living organisms to respond.
3. For example, if a man unintentionally touches a really hot object, he swiftly draws his hand away from it.
4. The stimulus in this case is hot, and the man responds by pulling his hand away from it.

Final answer: The reaction to a stimulus is called response.