Constant

A constant is a value that does not change. Commonly, a constant will be a real number, but can sometimes be written as a variable. When written as a variable, a constant is commonly denoted as c to represent a fixed value.

Example             y = 5x + 4

In the function above, 4 is a constant. The 5 is a fixed number, but it is more appropriate to call it a coefficient because it is multiplied by x.

Example           y = 9

The term "constant" may also refer to a constant function, or a function whose output value is the same for every input value. The function above is a constant function.

Example                       e,π, i, etc.

Some constants are given special symbols because they represent significant values and have important applications across different mathematical fields of study.