Fiber is fibrous material of animal, vegetable, mineral, or synthetic origin. Natural fibers can be made in yarn, textiles, and other products, including carpets, rope and felt. The fibers consist of long narrow cells. Animal fibers are based on protein molecules and include wool, silk, mohair, angora, and horsehair. Vegetable fibers are based mainly on cellulose and include cotton, linen, flax, jute, sisal, and kapok. The mineral asbestos is a natural inorganic fiber. Regenerated fibers are manufactured from natural products, modified chemically. For example, rayon is made from cellulose fiber obtained from cotton or wood.

Synthetic fibers are made from a molten or dissolved plastic resin by forcing it through fine nozzles (spinnerets). The result is a group of filaments that are wound onto bobbins. These fibers can be used as single-strand yarn, or spun to make multi-strand yarn. The yarn may be woven into textiles. Many textiles, particularly for clothing, use both synthetic and natural fibers woven together. Some synthetic fibers are made into rope, carpets, and other products. Synthetic fibers include nylon and other polyamides, polyesters, and acrylics. Nylon, the first synthetic fiber, was introduced in 1938. Other synthetic fibers, such as fiberglass, carbon, and metals, can be used to reinforce resins to produce extremely strong materials to be used in sports equipment, for example.