A cap or helmet is a type of HEADGEAR that is worn for protection, style, or both. It is typically made of hard material such as metal, plastic, or leather and can be used in a variety of settings, from sports to military operations. The term 'cap or helmet' is often used interchangeably to refer to any type of HEADGEAR, although there are subtle differences between the two. Caps are generally lighter and less protective than helmets, while helmets offer more coverage and protection.