A suit, lounge suit, or business suit is a set of clothes comprising a suit jacket and trousers of identical textiles generally worn with a collared dress shirt, necktie, and dress shoes. A skirt suit is similar, but with a matching skirt instead of trousers. It is currently considered semi-formal wear or business wear in contemporary Western dress codes, however when the suit was originally developed it was considered an informal or more casual option compared to the prevailing clothing standards of aristocrats and businessmen. The lounge suit originated in 19th-century Britain as sportswear and British country clothing, which is why it was seen as more casual than citywear at that time, with the roots of the suit coming from early modern Western Europe formal court or military clothes. After replacing the black frock coat in the early 20th century as regular daywear, a sober one-coloured suit became known as a lounge suit.

Formal wear or full dress is the Western dress code category applicable for the most formal occasions, such as weddings, christenings, confirmations, funerals, Easter and Christmas traditions, in addition to certain state dinners, audiences, balls, and horse racing events. Generally permitted other alternatives, though, are the most formal versions of ceremonial dresses, full dress uniforms, religious clothing, national costumes, and most rarely frock coats. In addition, formal wear is often instructed to be worn with official full size orders and medals.