A nightshirt is simply a reference to any shirt worn at night for sleeping in. The word nightshirt stems back to the 18th century when both men and women slept in the shirts or smocks that were worn under their normal clothing during the day. They would remove all their clothing and sleep only in the shirt. Today, a nightshirt is a word that is synonymous with nightgown and pajamas and is worn at night, but removed before dressing for the day.
For modern retail purposes, a nightshirt is usually a garment made of cotton or flannel, resembling a long T-shirt and is not the same as a nightgown, which may be made of cotton, silk, or any other material and is generally full length. The length of a nightshirt typically rests somewhere near the knees. A nightshirt is also usually short or long sleeved, but not sleeveless.
Though a nightshirt could simply refer to the top half of a set of pajamas, a nightshirt is generally a single garment and does not include pants or shorts. Most often, a nightshirt is designed to be slightly better fitting than a T-shirt to avoid twisting and bunching during sleep. Nightshirts are made for men and women, but are most commonly purchased by women, especially young girls.
Nightshirts featuring favorite commercial or cartoon characters are particularly popular amongst young girls, while older girls may prefer a nightshirt that has a trendy phrase or logo printed on it. Most nightshirts and other pajamas designed for children have some sort of flame retardant additive when sold where law requires it.
Adults often select a nightshirt made of cotton or flannel for their comfort and warmth while sleeping and nightshirts are convenient when making trips to the bathroom in the middle of the night. Though comfortable, practical, and sometimes designed to be somewhat feminine, depending on print, nightshirts are not usually considered to be a particularly sexy or promiscuous style of nightwear.