Underwear are clothes worn under other clothes, often next to the skin. They keep outer clothes from being made dirty by sweat. They also shape the body and provide support for parts of it, and in cold weather help the wearer to keep warm. Underwear can be used to protect the wearer's modesty, as well as to make them look sexy. Special types of underwear have religious importance. Some items of clothing are made to be worn as underwear, while others such as T-shirts and certain types of shorts can be used both as underwear and as outer clothing. If made of suitable fabric, some types of underwear can serve as nightwear or swimsuits.