A suit is a set of garments crafted from the same cloth, consisting of at least a jacket and trousers. Lounge suits are the most common style of Western suit, originating in England as country wear. Other types of suit still worn today are firstly the dinner suit, part of black tie, which arose as a lounging alternative to dress coats in much the same way as the day lounge suit came to replace frock and morning coats; and secondly, rarely worn today, the morning suit. This article discusses the lounge suit (including business suits), which is part of the 'informal' dress code.

The variations in design, cut, and cloth, such as two- and three- piece, or single- and double- breasted, determine the social and work suitability of the garment. Often, suits are worn, as is traditional, with a collared shirt and necktie. Until around the 1960s, as with all men's clothes, a hat would have been also worn when the wearer was outdoors. Suits also come with different numbers of pieces: a two-piece suit has a jacket and the trousers; a three piece adds a waistcoat; further pieces might include a matching flat cap.

Originally, as with most clothes, a tailor crafted the suit from his client's selected cloth; these are now often known as bespoke suits. The suit was custom made to the measurements, taste, and style of the man. Since the Industrial Revolution, most suits are mass-produced, and, as such, are sold as ready-to-wear garments (though alteration by a tailor prior to wearing is common). Currently, suits are sold in roughly three ways:

• bespoke, in which the garment is custom-made from scratch entirely for the customer, giving the best fit and free choice of fabric;
• made to measure, in which a pre-made pattern is modified to fit the customer, and a limited selection of options and fabrics is available;
• and finally ready-to-wear, which is least expensive and hence most common.