részhalmazreláció
The subset relation, denoted by $\subseteq$, is a fundamental concept in set theory. For any two sets A and B, A is considered a subset of B if and only if every element of A is also an element of B. This can be formally expressed as: $A \subseteq B \iff \forall x (x \in A \implies x \in B)$.
If set A contains at least one element that is not in set B, then A is
The subset relation is reflexive ($A \subseteq A$), antisymmetric (if $A \subseteq B$ and $B \subseteq A$,
A proper subset is a subset that is not equal to the original set. If $A \subseteq