Twill is a weave, not a fibre. Its threads pass over and under one another in a stepped sequence, creating the diagonal ribs visible on denim, gabardine and many tailoring fabrics. Cotton, wool, silk, viscose or synthetic yarns can all be woven this way, so two twills may feel completely different even though they share the same construction.
What the diagonal changes
Compared with a plain weave of similar weight, twill is often more supple, resistant to creasing and able to hide everyday marks. Look across the surface in good light: the diagonal should run evenly, without bowed lines or abrupt changes around seams. Dense twill gives trousers and jackets a clean shape; lighter versions move more softly and may show pressure shine sooner.
Check high-friction areas such as pocket edges, cuffs and the inner thigh. A strong twill should not already show broken yarns or a fuzzy ridge. Dark colours can reveal rubbing and washing through lighter diagonal lines, which is a natural part of ageing in some garments but a warning sign if it appears before wear.
Care
Read the fibre label first. Cotton twill may tolerate regular washing, while wool and silk qualities often need gentler or professional care. Wash dark garments inside out, avoid excessive spin and reshape seams while damp. Press from the reverse with a cloth; heavy heat on the face can flatten the rib and create gloss.
Choose twill for useful structure with freedom of movement. Judge it by fibre, density and finish rather than assuming that every diagonal fabric will perform like denim.
