What is the Difference Between Variable and Constant?

05/30/2025 • Matheus Moraes

The main difference between variables and constants lies in their values' ability to change. Here is a summary of their characteristics:

  • Constants:
  • Do not change their value as the equation is solved.
  • Usually written in numbers (fractions, integers, decimals, or real numbers).
  • Represent known values in an equation or expression.
  • Have fixed face values.
  • Variables:
  • Change their value depending on the equation.
  • Written as letters or symbols.
  • Represent unknown values in an equation or expression.
  • Do not have fixed face values.

In algebraic expressions and equations, constants are used to represent fixed values, while variables represent values that can change. For example, in the expression 3x + 5y = 7, the constant is 7, and the variables are x and y. Constants are often written in numbers, while variables are represented by letters or symbols.

Comparative Table: Variable vs Constant

Here is a table comparing the differences between variables and constants:

Feature Constants Variables
Definition A constant is a fixed value that cannot change during the program's execution. A variable is a data item whose value can change during the program's execution.
Value Constants have fixed values that do not change. Variables can have varying values depending on the context and can change over time.
Representation Constants are usually written in numbers or as literal constants (e.g., 'A', "Hello world!"). Variables are typically represented by letters or symbols.
Use Constants are used to store known values in an equation, expression, or line of programming. Variables represent unknown values in an equation, expression, or line of programming.
Example In an algebraic expression, the speed of light (c) is a constant with a fixed value of 299,792,458 meters per second. In an algebraic expression, the variable x can represent an unknown value that needs to be determined, such as the distance a car travels in a given time.

Constants are fixed values that do not change during the execution of a program, while variables are data items whose values can change during the program's execution. Constants are used to store known values, while variables represent unknown values that need to be determined.

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