Intersection

The intersection of two sets $A$ and $B$ is the set of elements common to $A$ and $B$. This is written $A\cap B$, and is pronounced ``$A$ intersection $B$'' or ``$A$ cap $B$.'' The intersection of sets $A_1$ through $A_n$ is written $\bigcap_{i=1}^n A_i$. The intersection of lines $AB$ and $CD$ is written $AB\cap CD$.

See also And, Union