Definition
Constant
A constant is a number or value that stays fixed in the mathematical situation being described.
What it means
A variable is allowed to change; a constant is the part that is staying put for this problem. In y = 4x + 7, x and y can change while 4 and 7 are fixed numbers. A letter such as c can also name a constant when its value has already been fixed.
Remember it
Constant means fixed for this situation—not fixed forever in every piece of mathematics.
Example
A taxi cost is C = 3m + 5, where m is the number of miles. The starting charge 5 is a constant because it stays 5 while m changes. The number 3 is also fixed here, but it is the coefficient of m; 5 is the constant term.
Watch for
In n + 4, n is not a constant when n is allowed to take different values; 4 is constant.
Common mix-up
A constant does not have to be written as a numeral. A letter can represent a constant after its value is fixed.
Exact meaning
A constant is a quantity whose value is fixed within a stated mathematical situation. It may appear as a number on its own, as the constant term of an expression, or as a named parameter; the same symbol can be constant in one situation and variable in another.