predictor variable

a variable in research that is believed may predict scores on another variable, called the dependent variable. Also called an "independent variable."

Imagine some researchers decide to investigate the relationship between time of day and air temperature: they have a hunch that if you know the time of day, you can predict the temperature. In this situation, the predictor variable is the time of day. The dependent variable is temperature.

They want to know if temperature depends on time of day.

Or to put it another way:

It is important to remember that the predictor variable might not actually predict anything at all. The point of the research is to find out if it does. Until the research is finished, it is called the predictor variable, even though its ability to provide predictions is not yet known.

Research can involve one or multiple predictor variables (for example, time of day combined with time of year).