A stimulus is anything that can trigger a physical or behavioral change. The plural of stimulus is stimuli.
Stimuli can be external or internal.
An example of external stimuli is your body responding to a medicine.
An example of internal stimuli is your vital signs changing due to a change in the body.
- Temperature changes
Taber's Medical Dictionary Online website. www.tabers.com/tabersonline. Accessed March 7, 2019.