1.3.3.1 Member (∈)

Suppose we have a set  and an element , if  is in , it is a member of or belongs to , denoted by   .

A few examples showing the member relation between a set and elements:

•  = {heads, tails}, then heads   and tails  
•  = {1, 2, 3, 4, 5, 6}, then 4  
• 1 , as 1 is one of the natural numbers.

Equivalently, when expressing in terms of sets, we can say that  contains , denoted by  ∋ . The previous examples can be represented as:

• {heads, tails} ∋ heads and {heads, tails} ∋ tails
• {1, 2, 3, 4, 5, 6} ∋ 4
•  ∋ 1