* Independent Variable (IV): This is the variable that the experimenter *manipulates* or changes. It's the "cause" in a cause-and-effect relationship.

* Dependent Variable (DV): This is the variable that is *measured* or observed in response to the independent variable. It's the "effect" in a cause-and-effect relationship.

* Controlled Variable (CV): These are all the other variables that need to be kept *constant* throughout the experiment to ensure that the observed changes in the dependent variable are solely due to the changes in the independent variable.

Here's an example:

Experiment: Does the amount of fertilizer affect plant growth?

* Independent Variable: Amount of fertilizer (the experimenter decides how much fertilizer to give each plant)

* Dependent Variable: Plant growth (measured by height, leaf size, etc.)

* Controlled Variables: Type of plant, amount of water, sunlight exposure, type of soil.

By keeping the controlled variables constant, the experimenter can be confident that any differences in plant growth are due to the different amounts of fertilizer (the independent variable).