\nsubseteqThe symbol \nsubseteq is used to denote that a set is not a subset of another set. In set theory, if A \nsubseteq B, it means that there exists at least one element in set A that is not present in set B, indicating that A is not entirely contained within B.
Set A is not a subset of set B.
A \nsubseteq BThe set \{1, 2, 3\} is not a subset of \{1, 2\} because it contains an element (3) not in the second set.
\{1, 2, 3\} \nsubseteq \{1, 2\}General notation indicating set X is not a subset of set Y.
X \nsubseteq Y