# Non-Member Relation

A Non-Member Relation is a Binary Relation between a Thing an a set.

**AKA:**Non-Member, ∉, NotIn,`\notin`

.**Context:**- It can be read as “
*x is not a member of set*”.**X** - It can be written as "[math] x \notin X[/math].”

- It can be read as “
**Example(s):**- A
*Snake*is a Non-Member of the*Mammal*set. - Non-Member(Snake,Mammal) ⇒
*True*.

- A
**See:**Member Relation, Subset Relation.