A waistcoat commonly called a vest in American English is a sleeveless upper-body garment. It is usually worn over a dress shirt and necktie and below a coat as a part of most men’s formal wear. It is also sported as the third piece in the traditional three-piece male business suit.
A waistcoat has a full vertical opening in the front, which fastens with buttons or snaps. Both single-breasted and double-breasted waistcoats exist, regardless of the formality of dress, but single-breasted ones are more common. In a three piece suit, the cloth used matches the jacket and trousers. Waistcoats can also have lapels or revers depending on the style.
Before wristwatches became popular, gentlemen kept their pocket watches in the front waistcoat pocket, with the watch on a watch chain threaded through a buttonhole. Sometimes an extra hole was made in line with the buttonholes for this use. A bar on the end of the chain held it in place to catch the chain if it were dropped or pulled. Waistcoats are now worn less, so the pocket watch may be more likely be stored in a trouser pocket