Set Theory

Definition of Set :

A set is an unordered collection of objects. We might also consume a set is a collection of object called element. 

Example :

In the circle above consist of a set of different shape of polygons. The polygons are the element of the set 

Other example are :
i.The students in this class
   >Students are the element in the set of class.
ii. People in office
   >People are the element in the set of office.


Reference : https://www.mathsisfun.com/definitions/set.html