Twill is a term referring to the diagonal pattern in which cloth is often woven. A fabric is twilled when two or more vertical threads -- the warp threads -- cross over two or more horizontal weft threads at a time. The result is a textile featuring a distinctively slanted pattern with a ribbed texture (known as wales). Twill can be crafted from any woven fiber -- including cotton, wool, silk -- and are most often used to make trousers and jeans.

Twill is more durable and resists wear longer than plain-weave fabric. It's also less prone to wrinkling and shrinkage. It provides superior resistance to moisture and cold. Twill also conceals dirt well. It drapes nicely and is easy to tailor.

Denim is a particular kind of cotton twill fabric, and so all denim jeans, no matter what their style, are classified as twill pants. Khakis and chinos, too, are typically constructed from a cotton or cotton-blend twill. Work pants often are constructed from a polyester or poly-blend twill. On the higher end of men's fashion, gabardine, serge and tweed are some twill fabrics that can be used in dress pants.