The intersection of two sets contains everything they share. If set A is {1, 2, 3, 4} and set B is {3, 4, 5, 6}, their intersection is {3, 4}. The symbol is ∩, so A ∩ B = {3, 4}.

Intersections appear in Venn diagrams as the overlapping region. In probability, the intersection of two events is the event that both occur. If the events are independent, the probability of the intersection is the product of their probabilities.

In geometry, the intersection of two lines is a point, of two planes a line, of a line and a plane a point. In database queries, intersection finds records common to two tables. The concept is simple but pervasive across mathematics and computer science.

• Set of common elements
• Symbol: ∩
• Shown as overlap in Venn diagrams
• Used in probability, geometry, and databases