This document provides an introduction to textile fibers. It defines a fiber as a delicate hair-like structure that can be natural or artificial. Fibers are characterized by flexibility, fineness, and a high length to thickness ratio. Textile fibers must be long enough, flexible, cohesive, and strong enough to be spun into yarns and made into fabrics. The most common textile fibers are made from the natural polymers cellulose and proteins, or the synthetic polymers polyamide, polyester, polyolefin, and acrylic.