## College Algebra (11th Edition)

$\emptyset\notin\emptyset$
$\emptyset$ is the empty set with no elements in it. Although $\emptyset$ and $\emptyset$ are both identical and are subsets of each other ($\emptyset\subset\emptyset$), they cannot be elements of one another because they have no elements. Therefore, $\emptyset$ is not an element of the empty set, written as $\emptyset\notin\emptyset$.