Subset
A set that contains only members of the given set,
\begin{equation*} A \subseteq B \iff \forall a \in A, \> a \in B. \end{equation*}A set that contains only members of the given set,
\begin{equation*} A \subseteq B \iff \forall a \in A, \> a \in B. \end{equation*}