Pants, slacks, and trousers are all terms used to describe a type of clothing item that is worn around the waist and covers the legs. Although these terms are often used interchangeably, there is actually a difference between them. Pants are usually made of denim or cotton and have a relaxed fit. Slacks are more formal than pants, usually made of wool or polyester, and have a more tailored fit. Trousers, on the other hand, can refer to either pants or slacks depending on context.