In the expression 3x + 7, the number 7 is a constant. It stays the same no matter what x is. The 3 is a coefficient, and x is a variable. Constants anchor expressions, giving them fixed points of reference.

Some constants are universal. Pi, approximately 3.14159, relates a circle's circumference to its diameter. e, approximately 2.71828, is the base of natural logarithms and appears in growth and decay problems. The speed of light, c, is a constant of physics. These named constants recur across many fields.

In algebra, constants are the terms without variables. In calculus, the derivative of a constant is zero because it does not change. In differential equations, constants of integration appear when solving indefinite integrals. The idea is simple, but it organizes a great deal of mathematics.

• Value that does not change
• Named constants include π and e
• Derivative of a constant is zero
• Constants of integration appear in calculus