\notinThe symbol \notin is used in mathematics to denote that an element is not a member of a set. It is the negation of the \in symbol, which indicates membership in a set. This symbol is commonly used in set theory and related fields to express that a particular object does not belong to a specified set.
Indicates that the element x is not in the set A.
x \notin AThe number 5 is not an element of the set containing 1, 2, 3, and 4.
5 \notin \{1, 2, 3, 4\}The element z is not in the empty set, which is always true since the empty set has no elements.
z \notin \emptyset