Difference Between Variable and Constant

Variable and constant are two commonly used mathematical concepts. Simply put, a variable is a value that is changing or that have the ability to change. A constant is a value which remains unchanged. Even though the concepts are fundamental in many aspects of mathematics, in elementary levels, it is used in algebra predominantly.


In the mathematical context, a variable is a quantity which has a changing or a variable magnitude. Commonly (in algebra), it is represented by an English letter or a Greek letter. It is common practice to call this symbolic letter the variable.

Variables are used in equations, identities, function, and even in geometry. Few of the use of variables are as follows. Variables can be used to represent unknowns in equations such as x2-2x+4=0. It also can represent a rule between two unknown quantities like y=f(x)=x3+4x+9. In probability and statistics, a random variable is a variable that can assume different states or events in the considered set of events. In mathematics, it is customary to emphasize the valid values for the variable, which is called the range. These limitations are deduced from the general properties of the equation or by definition.


Constants are often used to represent numbers with physical significance. In physics, chemistry, and any other natural science, you will encounter constants, which are specific letters assigned to represent values of quantities in nature or a mathematical theory. The Universal constant of Gravitation often symbolized by G and Plank’s constant symbolized by h are examples of both the usages. (NB. Planks number is not just a mathematical entity, but it has broad physical interpretations)

What is the difference between Variables and Constants?

  •  Variables are quantities with changing magnitude, hence can assume different values based on the application.
  • • Constants are quantities with unchanging values, and used to represent numbers with significance.
  • • Both constants and variables are represented algebraically by English or Greek letters.
  • • Constants are used to represent quantities in nature which are fixed, and the variables are used to represent unknowns.

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