What Is a Constant? Definition, Solved Examples

What Is a Constant in Math

In math, a constant is a fixed value that does not change and remains the same throughout a mathematical expression, equation, or problem. Constants are typically represented by letters or symbols and are used to represent specific numerical values or mathematical parameters. They are contrasted with variables, which can change and take on different values.

For example,

  1. π is a mathematical constant representing the ratio of the circumference of a circle to its diameter, approximately equal to 3.14159.
  2. In geometry, a triangle always has three sides, which is a constant characteristic of this geometric shape.

Constant in math definition

A constant is something that always stays the same and doesn’t change. Imagine it like your favorite color, which never changes—it’s always the same. In math, we have special numbers that are also constants. They have fixed values and never change. For example, the number 3 is a constant because it’s always 3, and it won’t become 4 or 5. Constants help us solve math problems and understand the world around us by giving us reliable values to work with.

What Is a Constant Term in Algebraic Expression?

In algebra, a constant term is a specific type of term within an algebraic expression. An algebraic expression is made up of various terms, and a constant term is one that does not contain any variables; it is a fixed numerical value that remains the same regardless of the variables’ values.

For example, in the algebraic expression “3x + 2y – 5,” the constant term is “-5” because it doesn’t have any variables (like x or y) attached to it. It’s a fixed number and always contributes -5 to the expression’s value.

Constant terms are significant in algebraic expressions because they represent the part of the expression that doesn’t depend on variables. They are often used to represent fixed values or constants in mathematical problems or equations.

Constant Numbers

Constant numbers can take various forms, including integers (whole numbers), fractions, decimals, and mathematical constants. They are used to represent known, unchanging quantities in mathematical equations and problems.

For example, the number 5 is a constant number because it represents a fixed quantity, and it doesn’t change. Similarly, well-known mathematical constants like π (pi) and e (Euler’s number) are also considered constant numbers because they have specific, unchanging values (approximately 3.14159 and 2.71828, respectively).

Constant vs. Variable

Aspect Constants Variables
Definition Fixed, unchanging values Values can vary
Numerical Value Specific and constant Can change
Examples π (pi), 5, -0.5, e, 2/3 x, y, z, a, b, c, …
Role in Equations Provide fixed parameters Represent varying values
Consistency Do not change within context Can change based on conditions
Use in Modeling Represent fixed quantities Represent changing quantities
Common Operations Operate as constants Subject to mathematical operations
Significance Crucial in math and science Important in problem-solving
Examples in Math Circumference of a circle, Linear equations, quadratic
laws of physics, math equations, polynomial
constants functions, etc.

Solved Examples on Constants

Example 1: Solve the equation for the circumference of a circle, C, when the radius, r, is a constant of 5 units.
C = 2πrC=2πr

Substitute the constant value of the radius, r = 5, into the formula:
C = 2π(5) = 10π

So, when the radius is a constant of 5 units, the circumference of the circle is 10π units.

Example 2 Find the constant in the algebraic expression 3x + 5


Given expression: 3x + 5

The only term that is fixed is 5.

So, the constant is 5.

Example 3: Suppose you have a car traveling at a constant speed of 60 miles per hour. How far will it travel in 3 hours?

Solution: Use the formula for distance, which involves a constant speed:


D=60 miles per hour×3 hours=180 miles

So, when the car is moving at a constant speed of 60 miles per hour, it will travel 180 miles in 3 hours.


1. What is the difference between a coefficient and a constant?

A coefficient is a numerical factor that is multiplied by a variable in an algebraic expression or polynomial. It is a value that can change depending on the specific equation or context. For example, in the term “3x,” the coefficient is 3.
A constant, on the other hand, is a fixed value that does not depend on variables. It remains the same within a given context or equation. Constants are specific numerical values. For example, in the expression “2 + 5,” both 2 and 5 are constants.
2. Can a constant be negative?

Yes, constants can be negative. For example, -3, 0, and 7 are all constants.
3. What is a constant polynomial?

A constant polynomial is a polynomial that consists of only a constant term and no variable terms.
4. Is 0 a constant?

Yes, 0 is a constant. It is a specific numerical value that does not change.