Nightwear, also called "sleepwear", "sleeping suit", "nightclothes", or "nightdress", is clothing

Clothing

Clothing refers to any covering for the human body that is worn. The wearing of clothing is exclusively a human characteristic and is a feature of nearly all human societies...

 designed to be worn while sleep

Sleep

Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...

ing. The style of nightwear worn may vary with the seasons, with eg. warmer styles being worn in colder conditions. Some styles or materials are selected to be visually appealing or erotic, sometimes in addition to their functional purpose of warmth.

Examples of types of items of nightwear include:

• Babydoll
  Babydoll
  A babydoll is a short, sometimes sleeveless, loose fitting nightgown or negligee intended as nightwear for women. It sometimes has formed cups called a bralette for cleavage with an attached loose fitting skirt falling in length usually between the upper thigh and the belly button...
  
   - a short, sometimes sleeve
  Sleeve
  Sleeve is that part of a garment which covers the arm, or through which the arm passes or slips. The pattern of the sleeve is one of the characteristics of fashion in dress, varying in every country and period...
  
  less, loose-fitting nightgown or negligee for women, generally designed to resemble a young girl's nightgown.
• Blanket sleeper
  Blanket sleeper
  The blanket sleeper is a type of especially warm sleeping garment worn primarily during the winter in the United States and Canada...
  
   - a warm sleeping garment for infant
  Infant
  A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
  
  s and young child
  Child
  Biologically, a child is generally a human between the stages of birth and puberty. Some vernacular definitions of a child include the fetus, as being an unborn child. The legal definition of "child" generally refers to a minor, otherwise known as a person younger than the age of majority...
  
  ren.
• Chemise
  Chemise
  The term chemise or shift can refer to the classic smock, or else can refer to certain modern types of women's undergarments and dresses...
  
   - when used in reference to sleepwear, it is a delicate, usually provocative, loose-fitting, sleeveless, shirt-like lingerie
  Lingerie
  Lingerie are fashionable and possibly alluring undergarments.Lingerie usually incorporates one or more flexible, stretchy materials like Lycra, nylon , polyester, satin, lace, silk and sheer fabric which are not typically used in more functional, basic cotton undergarments.The term in the French...
  
  , similar to babydoll, but tighter at the hips.
• Funzee - an all-in-one sleepsuit worn by adults but similar to an infant onesie, usually made from cotton.
• Negligee
  Negligee
  The negligee is a form of women's clothing consisting of a sheer usually long dressing gown. It is a form of nightgown intended for wear at night and in the bedroom...
  
   - loose, sensuous nightwear for women usually made of sheer or semi-translucent fabrics and trimmed with lace
  Lace
  Lace is an openwork fabric, patterned with open holes in the work, made by machine or by hand. The holes can be formed via removal of threads or cloth from a previously woven fabric, but more often open spaces are created as part of the lace fabric. Lace-making is an ancient craft. True lace was...
  
   or other fine material, and bows.
• Nightgown
  Nightgown
  A nightgown is a loosely hanging item of nightwear. Nowadays the term is almost exclusively applied to women's nightwear. A nightgown is typically made from cotton, silk, satin, or nylon...
  
   - loose hanging nightwear for women, typically made from cotton
  Cotton
  Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
  
  , silk
  Silk
  Silk is a natural protein fiber, some forms of which can be woven into textiles. The best-known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity...
  
  , satin
  Satin
  Satin is a weave that typically has a glossy surface and a dull back. It is a warp-dominated weaving technique that forms a minimum number of interlacings in a fabric. If a fabric is formed with a satin weave using filament fibres such as silk, nylon, or polyester, the corresponding fabric is...
  
  , or nylon
  Nylon
  Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...
  
  .
• Nightshirt
  Nightshirt
  A nightshirt is a garment intended for sleeping in. It is somewhat longer than most regular shirts, reaching down to the thighs or below the knees, leaving some of the legs uncovered. It is generally loose-fitting to avoid restricting the wearer's movement while sleeping....
  
   - loose-fitting garment, longer than a regular shirt
  Shirt
  A shirt is a cloth garment for the upper body. Originally an undergarment worn exclusively by men, it has become, in American English, a catch-all term for almost any garment other than outerwear such as sweaters, coats, jackets, or undergarments such as bras, vests or base layers...
  
  .
• Nightcap
  Nightcap (garment)
  A nightcap is a warm cloth cap worn while sleeping, often with pajamas or a nightgown. They are similar to winter 'beanies' worn in cold climates. They were common in northern Europe before central heating was available, when homes were cold at night....
  
   - a warm cloth cap
  Cap
  A cap is a form of headgear. Caps have crowns that fit very close to the head and have no brim or only a visor. They are typically designed for warmth and, when including a visor, blocking sunlight from the eyes...
  
   sometimes worn by women or men with pajamas or a nightgown.
• Peignoir
  Peignoir
  A peignoir is a long outer garment for women frequently sheer and made of chiffon or other translucent fabrics. The word come from French peigner, to comb the hair describing a garment worn while brushing ones hair, originally referring to a dressing gown or bathrobe...
  
   - a long outer garment for women usually sheer and made of chiffon
  Chiffon (fabric)
  Chiffon, , from the French word for a cloth or rag, is a lightweight, balanced plain-woven sheer fabric woven of alternate S- and Z-twist crepe yarns. The twist in the crepe yarns puckers the fabric slightly in both directions after weaving, giving it some stretch and a slightly rough...
  
  . They are usually sold with a matching nightgown, negligee or panties
  Panties
  Panties are a form of underwear, usually light and snug-fitting, designed to be worn by women or girls in the area directly below the waist. Typical components include an elastic waistband, a crotch panel to cover the genital area , and a pair of leg openings which, like the waistband, are often...
  
   but are often worn with no underwear.
• Pajamas
  Pajamas
  Pajamas, also spelled pyjamas , can refer to several related types of clothing. The original paijama are loose, lightweight trousers fitted with drawstring waistbands and worn in South and West Asia by both sexes...
  
   - loose fitting two-piece garments for women, men and children. They may be made from cotton, silk
  Silk
  Silk is a natural protein fiber, some forms of which can be woven into textiles. The best-known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity...
  
  , satin
  Satin
  Satin is a weave that typically has a glossy surface and a dull back. It is a warp-dominated weaving technique that forms a minimum number of interlacings in a fabric. If a fabric is formed with a satin weave using filament fibres such as silk, nylon, or polyester, the corresponding fabric is...
  
   or synthetic materials.

There are several other types of garment that are commonly worn for sleeping – especially clothing otherwise used for physical education, see next section – but these are usually not referred to as nightwear, because they may also be worn during the day and in public. Also, sleeping without any clothing at all is not uncommon.

Customs

According to a 2004 United States survey, 13% of men wear pajamas or nightgowns for sleeping, whereas 31% wear underwear and another 31% sleep nude. Among women, 55% wear pajamas or nightgowns, which were counted under the same option:

What worn for sleeping	Men (%)	Women (%)	All (%)
Nothing/nude Nudity Nudity is the state of wearing no clothing. The wearing of clothing is exclusively a human characteristic. The amount of clothing worn depends on functional considerations and social considerations...	31	14	22
Underwear	31	2	16
Nightgown Nightgown A nightgown is a loosely hanging item of nightwear. Nowadays the term is almost exclusively applied to women's nightwear. A nightgown is typically made from cotton, silk, satin, or nylon... /Pajamas Pajamas Pajamas, also spelled pyjamas , can refer to several related types of clothing. The original paijama are loose, lightweight trousers fitted with drawstring waistbands and worn in South and West Asia by both sexes...	13	55	34
Shorts Shorts Shorts are a bifurcated garment worn by both men and women over their pelvic area, circling the waist, and covering the upper part of the legs, sometimes extending down to or even below the knee, but not covering the entire length of the leg. They are called "shorts" because they are a shortened... /t-shirt T-shirt A T-shirt is a style of shirt. A T-shirt is buttonless and collarless, with short sleeves and frequently a round neck line....	21	25	23
Sweatshirt/sweatpants	1	2	1
Something else	3	1	2
No opinion	1	1	1

A survey by the BBC

BBC

The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...

 The Clothes Show

The Clothes Show

The Clothes Show is a British television show about fashion that can currently be seen weeknights on Really. It was formerly broadcast on BBC One from 1986 to 2000.-BBC series :...

Magazine in 1996 revealed the following about sleepwear in the UK

%	Pyjamas	Nothing	Underwear	Nightdress	Other
Women	37	17	9	33	4†
Men	6	47	22	-	25†

†Most common response in 'Other' from women was outdoor clothes, from men shorts.