In a scientific experiment, the dependent variable--sometimes called the outcome variable--measures the effect of whatever experiment you've performed. For example, if you're studying the effects of fertilizer on plant growth, your dependent variable would be the height of the plant. (The amount of fertilizer you gave would be the independent variable.)

People sometimes confuse independent and dependent variables, but there's a mnemonic that will allow you to remember the difference. In any given experiment, you're looking to see if one variable depends on the value of another variable. In the above example, plant height depends on something else, so it's the dependent variable.

In Mathematics, dependent variable is a number-variable whose value is to be determined by another number-variable. In the example:

y=3x

"y" is the dependent variable. Its value is dependent on the value of "x" (i.e., y varies, depending on the value of x).