# What does the mathematical expression 9 ∉ T mean?

Dec 14, 2015

$9 \notin T$ means that $9$ is not an element of the set $T$.

#### Explanation:

The symbol $\notin$ is used with a set $S$ and a potential element $a$ of $S$ to mean

$a \notin S$

if and only if $a$ is not an element of $S$. Some people like to say that $a$ "does not belong" to set $T$.

(compare to $\in$ which implies an element is in a set)

Thus $9 \notin T$ means that $9$ is not an element of the set $T$