# Set theory

(Redirected from Introduction to set theory)

## Welcome!

 Resource type: this resource is a lesson.

Welcome! This is a lesson in the Computer Science course Introductory Discrete Mathematics for Computer Science.

## Basic Definition

Intuitively, a set can be thought of as a collection of elements. In a set, the order of the elements is irrelevant, as is the possibility of duplicate elements. For example, we write $X = \{ 1, 2, 3 \}$ to denote a set $X$ containing the numbers 1, 2 and 3. Or, $X = \{ 1, 2, 3 \} = \{3,2,1 \} = \{1,1,2,3,3\}$.