$\cap$

The intersection of two sets is the set consisting of only the elements that appear in both sets.

• $A \cap B$ denotes the intersection of sets $A$ and $B$.
  • ex. $G \cap D = \{Alice\}$ means that "Alice is a part of both set $A$ and set $B$".

Two sets whose intersection is the empty set (in other words, have no element in common) are called disjoint.

Example: Yelp

• $A =$ The set of Yelp users who like Biz1
• $B =$ The set of Yelp users who like Biz2

The set $A \cap B$ is the set of users that liked both Biz1 and Biz2