What does variables mean in scientific terms?

Answer 1

A variable is something that can be changed.

To vary is to change, and a variable is something that can change, particularly if it is a parameter of a scientific experiment. If you are, let us say, testing the effect that a drug has on rats, the most obvious variable would be the quantity of the drug which is administered to the rats. But there could be many other variables in this hypothetical experiment. Rats come in different sizes, ages, and genders; they can be overweight or underweight, they can be healthy or unhealthy. All of those are variables. You could alter the temperature of the environment in which the rats are being tested, or alter their diets; those are also variables. You would not necessarily want to devise different experiments to test the effects of all these variables; it is up to you to decide what interests you or what matters in terms of your research.