For any two [[Set|Sets]] $A, B$: $A$ is a [[Subset]] of $B$ if every element of $A$ is also an element of B $\huge A \subset B \iff { \forall x (x\in A \rightarrow x \in B) } $ >[!example]- Subsets with [[02 Areas/Math/Sets of Numbers]]. >$\huge >\N \subset \Z^{+} \subset \Z \subset \Q \subset \R \subset \C >$