Subset of a set – Sets:

Let A be the set of states in India and let B be the set of all states in South India. We know B = {Karnataka, Andra Pradesh, Kerala, Tamil Nadu}. Karnataka is the element of B, but Karnataka is also a state of India.  So, Karnataka is also an element of A. Similarly, Andra Pradesh, Kerala, Tamil Nadu are also state in India.  Thus every element of B is an element of A. In such situation we say B is subset of A. So, given a set A, as set B is called subset of A if every element of B is also an element of A.

It can be written as B⊂ A