Answer:
A variable is the factor that changes in a controlled experiment.
Step-by-step explanation:
There are usually three variable in an experiment: the constant, the independent variable, and the dependent variable.
Take this experiment for example: Seeing if different amounts of light impact the growth of a plant.
CONSTANT: the plant
INDEPENDENT VARIABLE: the amount of sunlight
DEPENDENT VARIABLE: the growth of the plant (this depends on the sunlight the plant is receiving.)