Nightwear, also called "sleepwear", "nightclothes", or "nightdress", is clothing designed to be worn while sleeping. It is generally worn otherwise only in the company of those one knows well. Some people do not use nightwear at all, preferring to sleep nude or in some kind of underwear. Some nightwear usage is seasonal, i.e. some persons only wear nightwear in winter. (See also List of types of clothing and Clothing terminology) Humans nearly universally wear articles of clothing (also known as dress, garments, or attire) on the body. ... A human female sleeping Sleep is the regular state of natural unconsciousness observed in all mammals and birds. ... The word nude may refer to: The state of nudity. ... A pair of mens briefs Undergarments, also called underwear or sometimes intimate clothing, are clothes worn next to the skin, usually under other clothes. ... In many parts of the world, winter is associated with snow. ...