Stimulus (physiology) , in physiology, is something external that elicits or influences a physiological or psychological activity or response
In Psychology , anything effectively impinging upon any of the Sensory apparatuses of a living organism, including physical phenomena both internal and external to the body.
Stimulation , the action of various agents (stimuli) on muscles, nerves, or a sensory end organ
In other fields, a stimulus is anything that may have an Impact on a system; an Input to the system. (E.g., an Economic stimulus.)
Although related, the word's meaning is distinct from that of " Stimulant ."
