1. anything that contributes to a result or has a causal relationship to a phenomenon, event, or action.

2. an underlying influence that accounts in part for variations in individual behavior.

3. in analysis of variance and other statistical procedures, an independent variable.

4. in factor analysis, an underlying, unobservable latent variable thought (together with other factors) to be responsible for the interrelations among a set of variables.

5. in mathematics, a number that divides without remainder into another number.