1) A relationship between a class of responses and a class or classes of stimuli. Implies nothing about the nature of the relationship or its effects.

2) A dependency or a causal relationship.

3) In the operant case, the conditions under which a response produces a consequence (e.g., in an FI, the reinforcer is said to be contingent on a response of a given force, topography, etc., as well as on the passage of time). An organism is said to come into contact with a contingency when its behaviour produces some consequences of the contingency.

4) In respondent conditioning, contingency refers to a correlation between CS and US. Rescorla (1972) has suggested that a positive correlation between CS and US, rather than the mere pairing of these stimuli, is necessary for conditioning. For operant conditioning, see contingency of reinforcement.

5) The relationship between a kind of response, the stimuli which precede it, and the stimuli which follow. All three terms must be specified in a complete statement of a contingency. The plural of contingency is contingencies, or contingencies of reinforcement.

6) That is not direct acting. Either an indirect acting contingency or an ineffective contingency.

7) The term contingency also applies to respondent cases, referring to the conditions under which some stimuli are followed by others. By analogy to the operant case, stimulus-stimulus contingencies expressed as conditional probabilities specify conditions more completely than descriptions in terms of pairings or temporal contiguities, distinguishing cases in which two stimuli always occur together from those in which they are frequently paired but also occur independently of each other; and stimuli correlated with stimulus-stimulus contingencies (sometimes called occasion setters) may enter into three-term or higher-order relations.