1) A variable that is measured while another variable (the independent variable) is changed in a systematic way. When systematic changes in the independent variable are accompanied by changes in the dependent variable, we say that the two are functionally related-that the level or value of the dependent variable is in fact dependent on the level or value of the independent variable. In applied behaviour analysis, the dependent variable usually is behavior; the independent variable some condition or treatment that may affect the level of that behavior.

2) In behavioural science the dependent variable is usually that behaviour of the organism which changes as a function of its interaction with the environment (the independent variable).

3) The variable that may change depending on the presence or absence of the independent variable. In the study of behavior, usually a response class.

4) What is measured in an experiment, commonly called an effect. In behaviour analysis, the dependent variable is the behaviour of organisms.