Subset

Symbol: $\subseteq$

Let $A$ and $B$ be Sets. We say $A$ is a subset of $B$ (and write $A\subseteq B$) if every element of $A$ is also an element of $B$. For example, the set of all integers is a

$A\subseteq B$ is true, if all elements of $A$ are within $B$.

Related: Proper Subset