Variable: a factor in a scientific experiment that may be subject to change
Now let's talk about what that means in practical terms. We can think of variables as the concepts/constructs of interest in research. Variables can be anything from tangible objects to more abstract ideas. Variables can be simple or they can be complex. In fact, the nature of what a variable is depends a lot on how that variable is defined and measured.
This term, operational definition, refers to a set of specific procedures that the researcher is going to follow in order to measure a given variable. This description is pivotal in making abstract concepts more concrete and measurable. It also allows you to make comparisons across research that involves the same variables. Different operational definitions could explain differences in findings, for instance.