"The reliable production of a response by a stimulus" (Catania, 1998, p. 8).
"A response component of a reflex; behavior that is elicited, or induced, by antecedent stimuli" (Cooper et al, 2007, p. 703).
"Behavior that is selected, maintained, and brought under stimulus control as a function of its consequences" (Cooper et al, 2007, p. 701).
"The reliable production of a response by a stimulus" (Catania, 1998, p. 8).
"A situation in which the frequency, latency, duration, or amplitude of a behavior is altered by the presence or absence of an antecedent stimulus" (Cooper et al, 2007, p. 705).
"An operant that occurs more frequently under some antecedent conditions than under others" (Cooper et al, 2007, p.694).
"A stimulus in the presence of which responses of some type have been reinforced and in the absence of which the same type of responses have occurred and not been reinforced" (Cooper et al, 2007, p. 694).
"...when a response consistently occurs in the presence of a specific or controlling antecedent stimulus and not in the presence of new or related stimuli. This is in direct contrast to stimulus generalization in which related antecedent stimuli may evoke the same response" (Cooper et al, 2007, pp. 395-396).