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.