What is Variable?

An entity which doesn’t have a fixed value instead have many values is known as a Variable.

For example:

Let A be a set and suppose x∈A or x is a element of set A.

by x∈A , we don’t mean  x is a element of set A instead we mean x is a representative for elements of set A.

so , x doesn’t have a fixed value or only one value instead it have many values. Like if set A={1,2,3} then the value of x is 1 , 2 and 3.

In the above example “x” is a variable in x∈A.

What is constant?

An entity which have a fixed value is known as a Constant.

For example:

Let B be a singleton set or B have only one element and y∈B.

So, as B have only one element thus y also have only one fixed value.

Thus, “y” is a constant in y∈B