The term variable means something that can ‘vary’ or ‘change’. The value of the variable can change. It can have different values. It is not fixed. We use variables in algebraic expressions when the quantity of something is unknown.

**Demonstration:**

Let us consider Ratan’s monthly salary plus Rs.300. But when we do not know his salary we can write it as

X+300

where X represents Ratan’s monthly salary.

Algebraic expressions and algebraic equations can contain more than one variable.

For example, 2×(*x* + y) is an algebraic expression that contains two variables, x and y .