Natural fibers come from plants and animals and are either spun or twisted into yarns. We are most familiar with cotton and wool, but other common thread products are made from silk, hemp, jute and linen (flax).
Synthetic fibers are made from various chemicals or a combination of chemicals and natural products. Rayon is made from cellulose acetate and other chemicals and forced through small holes to form individual fibers. Other synthetic fibers are polyester, acrylic and nylon. In most cases, a synthetic fiber has greater strength than a natural fiber, but this is not a blanket statement. The method of processing and quality of raw materials greatly affect strength in threads.
All fibers are formed into threads from either staple or continuous filaments. Staple refers to the length of the fiber. The term long staple usually refers to a smoother, stronger thread. Short staple thread usually has a fuzzy appearance and has less strength. Extra-long staple thread has the least amount of fuzz and has the most strength out of the staple measurement. Continuous filament refers to synthetic fibers of indefinite length.