A cap is a form of headgear. Caps have crowns that fit closer than hats and have no brim or only a visor. They are typically designed for warmth and, when including a visor, blocking the sun from the eyes.
Cap - Types of caps.
Baseball cap
Beanie
Beret
Biretta
Cap of maintenance
Coif
Combination cap (also known as service cap)
Flat cap
Kepi
Newsboy cap
Tam
Tubeteika
Tuque
Yarmul ...