Something causing or regarded as causing a response.
An agent, action, or condition that elicits or accelerates a physiological or psychological activity or response.
Something that incites or rouses to action; an incentive: "Works which were in themselves poor have often proved a stimulus to the imagination"(W.H. Auden).
Main Entry: stim·u·lus Pronunciation: 'stim-y&-l&s Function: noun Inflected Form: pluralstim·u·li/-"lI,-"lE/ 1:STIMULANT 1 2: an agent (as an environmental change) that directlyinfluences the activity of living protoplasm (as by exciting a sensory organ or evoking muscular contraction or glandular secretion) stimulus>
Physiology Something that can elicit or evoke a physiological response in a cell, a tissue, or an organism. A stimulus can be internal or external. Sense organs, such as the ear, and sensory receptors, such as those in the skin, are sensitive to external stimuli such as sound and touch.
Something that has an impact or an effect on an organism so that its behavior is modified in a detectable way. See more at classical conditioning.