A constant is a value that does not change or vary in a mathematical expression or equation. It is the opposite of a variable, which can take on different values. Constants can be numbers, symbols, or even functions that remain unchanged throughout a given problem or context.

For example, in the equation , and are constants, while and are variables. The number is the coefficient of the variable , and is a constant term.

Constants can also be symbols that represent specific values, such as (approximately ), which is the ratio of a circle’s circumference to its diameter, or (approximately ), the base of the natural logarithm.

A variable is a core concept in algebra where a symbol, usualy a lower case latin letter, is used as a placeholder in a math expression.

A coefficient is a numerical or constant quantity placed before and multiplying the variable in an algebraic expression.