In statistics, a covariate is a variable that is possibly predictive of the outcome under study. A covariate may be of direct interest or it may be a confounding or interacting variable.
The alternative terms explanatory variable, independent variable, or predictor, are used in a regression analysis. In econometrics, the term “control variable” is usually used instead of “covariate”.
In a more specific usage, a covariate is a secondary variable that can affect the relationship between the dependent variable and other independent variables of primary interest.