# Variables - Why use letters?

## Variables and Constants in Algebra

Understanding the purpose of variables and constants is essential for making progress in algebra. A variable is a symbol that represents a value or a number while a constant is a fixed number whose value will never change within an expression. For example, in the following polynomial, x is a variable and 4 is a constant.

#### Why Use Variables?

Variables can be incredibly helpful when solving a problem or representing long numbers more simply. For example, today, we know the speed of light to be 299,792,458 meters per second. Rather than writing this number out over and over again, scientists use the variable "c" instead. This saves a bunch of time!