Lapel

Lapels are the folded flaps of cloth on the front of a jacket or coat, and are most commonly found on formal clothing and suit jackets. Usually they are formed by folding over the front edges of the jacket or coat and sewing them to the collar, an extra piece of fabric around the back of the neck.

There are three basic forms of lapels: notched, peaked and shawl. Notched lapels, the most common, are usually seen on business suits. Peaked lapels are more formal, and nearly always used on double breasted jackets, but it also frequently appears on single breasted ones . Shawl lapels are usually carried by dinner jackets, mess jackets and tuxedos.

The notched lapel (American English), step lapel or step collar (British English) is sewn to the collar at an angle, creating a step effect. This is the standard on single-breasted suits, and is used on nearly all suit jackets, blazers, and sports jackets. The notched lapel double-breasted jacket is a rare setting. The size of the notch can vary, and a small notch is called fishmouth. This was the first type of lapel to appear.

The peaked lapel (American English), peak lapel, double breasted style lapel or pointed lapel (British English), is the most formal, featuring on double-breasted jackets, all formal coats such as a tailcoat or morning coat, and also commonly with a tuxedo (both single and double breasted). In the late 1920s and 1930s, the single breasted peaked lapel jacket was considered a very stylish design. The feature was carried into day clothing by the increasing popularity of the peaked dinner jacket. The ability to cut peak lapels properly on a single-breasted suit is one of the most challenging tailoring tasks, even for very experienced tailors.

The shawl lapel, roll collar, or shawl collar is a continuous curve. Originally seen on the Victorian smoking jacket, it is now most common on the dinner jacket or tuxedo. This similarly began as informal eveningwear, and was then made in both more and less formal versions, depending on the situation in which it was to be used. It is also commonly used on the mess jackets.

...
Wikipedia