Cap is a name for the symbol 
,
used for the intersection of sets,
and sometimes also for the logical connective AND instead
of the symbol 
(wedge). In fact, for any two sets 
and 
 |
and this equivalence demonstrates the connection between the set-theoretical and the logical meaning.
The term "cap" is also used to refer to the topological object produced by puncturing a surface a single time, attaching two zips around the puncture in opposite directions, distorting the hole so that the zips line up, and then zipping up. The cap is topologically trivial in the sense that a surface with a cap is topologically equivalent to a surface without one.
In solid geometry, a cap can also mean an end face of a cylinder. The caps of a right circular cylinder are its two end disks. A spherical cap is a region of a sphere cut off by a plane.
