**Elements Of a Set**

An element is a member of a set

Notation:

∈ means **“is an element of”**

∉ means **“is not element of”**

Example:

A = {positive integers between −3 and 3}

A = {1, 2}

1 ∈ A {1 is an element of A}

2 ∈ A {2 is an element of A}

3 ∉ A {3 is not element of A}

**Cardinality**

The cardinality of a set states the number of elements a set contains

The cardinality is expressed as n(A)

Example:

A = {days of the week}

A = {sunday, monday, tuesday, wednesday, thursday, friday, saturday}

n(A) = 7 {The number of elements of set A is 7}