# What is set theory

Dear Student,

A detailed solution to your query is provided below :

A

**set**is a collection of

__objects.There are are often specified with curly brace notation.__

*distinct***- {1, 2, 3} . The study of these sets and their relationships comes under Set Theory.Various important terms and defination included in Set Theory are :**

*for example*1

__is a set containing no objects. It is written as a pair of curly braces with nothing inside { } or by using the symbol ∅.__

**.Empty set -**2.

__- ∈ is used to say that an object is a member of a set. Example - If S = {1, 2, 3} then 3 ∈ S .__

**The set membership symbol**3.The

**cardinality**of a set is its size. For a finite set, the cardinality of a set is the number of members it contains.

4.The

**intersection of two sets**S and T is the collection of all objects that are in both sets. It is written S ∩ T . Using curly brace notation S ∩ T = {x : (x ∈ S) and (x ∈ T )}

5.The

**union of two sets**S and T is the collection of all objects that are in either set. It is written S ∪ T . Using curly brace notion S ∪ T = {x : (x ∈ S) or (x ∈ T )}

Regards.

**
**