A

David

Darling

cap

In mathematics, a cap is the symbol ∩, used to denote the intersection between two sets. Thus the intersection between sets P and Q is written as P ∩ Q. This is illustrated in a Venn diagram as the region of overlap between two sets.

 

The cap was first used as the symbol for intersection by Guiseppe Peano in Calcolo Geometrico secondo l'Ausdehnungslehre di H. Grassmann (1888). See also union.