independent variable

A factor or phenomenon that causes or influences another associated factor or phenomenon called a dependent variable.

For example, income is an independent variable because it causes and influences another variable consumption. In a mathematical equation or model, the independent variable is the variable whose value is given. In an experiment, it is the controlled condition (that is allowed to change in a systematic manner) whose effect on the behavior of a dependent variable is studied. Also called controlled variable, explanatory variable, or predictor variable.