What is the easiest way to define a dependent and independent variable in science?

An independent variable is exactly what it sound like. It is a variable that stands alone and is not changed by the other variable you are trying to measure. For example, someone's age might be an independent variable.

A dependent variable is exactly what it sound like. It is something that de[pends on other factors

For example, a test score is an dependent variable you got sleep at night before you took the test.

An independent variable is the variable that is changed. A dependent variable is the variable being tested and measured.