The Lesson
A constant is a number with a fixed value - its value does not change.Dictionary Definition
The Merriam-Webster dictionary defines a constant as "a number that is assumed not to change value in a given mathematical discussion."Real Examples of Constants
In algebra, some values always stay the same. They are constants. Numbers are examples of constants - a number can only have one value. 2 can only have a value of 2.

Understanding Constants
It is easier to understand constants with an example. Let's look at an algebraic equation. Consider a linear equation:
x = 1 ∴ y = 2x + 1 = 2 × 1 + 1 = 3
x = 2 ∴ y = 2x + 1 = 2 × 2 + 1 = 5
x = 3 ∴ y = 2x + 1 = 2 × 3 + 1 = 7
The constants are the same in each case and show which pairs of x and y are allowed by the equation.
Different constants would mean different pairs of x and y would be allowed by the equation.
Coefficients Are a Type of Constant
A constant in front of a variable is called a coefficient. For example, consider the equation shown below: