A stimulus is anything that can trigger a physical or behavioral change. The plural of stimulus is stimuli.
Stimuli can be external (a patient responds to a medication) or internal (a patient’s vital signs change due to a change in a bodily system).
Examples of stimuli include irritants, sights, sounds, heat, cold, smells, or other sensations.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.