# Variable (Mathematics)

Last Updated: August 18, 2011

## Definition - What does Variable (Mathematics) mean?

In mathematics, a variable is a quantity that can change. Letters are used to represent these changing, unknown quantities.

Einstein’s famous equation E = MC2 uses the following variables:
1. E for the amount of energy produced,
2. M for the amount of mass used, and
3. C2 to represent the speed of light squared.

Variables, unknown quantities, are the opposite of constants, which are known, unchanging amounts.

## Techopedia explains Variable (Mathematics)

Variables can be independent or dependent. Dependent and independent variables are commonly used in statistical studies and to control (to some degree) the outcomes of experiments. In the simple equation y = 2x, the letter x can be any real number. The value of y is completely dependent on the value chosen for x, and is always twice as much. Thus, x is the independent variable, and y is the dependent variable.

Variables are also used in computer programming. Typically, variables are assigned a data type, like numerical, alphabetical, image, array or video clips. Variables are also assigned memory locations. The data in the location can change during the execution of the program but the when the variable is encountered in the program, the computer substitutes the information in the correct memory location for the variable.