What is the term for anything that triggers a response?

• A. Trigger
• B. Signal
• C. Stimulus
• D. Prompt

Answer: (C)

Stimulus is anything that triggers a response. It can be external, like a loud sound or bright light, or internal, like hunger or a hormone change. The idea is that a stimulus provides the input that elicits a reaction from the organism, while the actual action you see is the response. Everyday terms like signal, prompt, or trigger pop up in different contexts, but stimulus is the precise term for any cue that leads to a reaction. A signal conveys information, a prompt cues someone to act, and a trigger is a more informal word for something that starts a reaction; stimulus covers all these possibilities and is the standard scientific term.