Belong to. The use of clothing can be divided into two categories: underwear and outerwear. Coat is worn in different places and has different uses. There are many varieties, including social clothing, daily clothing, professional clothing, sports clothing, indoor clothing, stage clothing and so on. But underwear plays a role in protecting the body, keeping warm, shaping and living, so pajamas are classified as underwear. Paejama, the original word of pajamas, comes from Hindi and is a combination of pai and jamah in Persian.