In most cases, a synthetic fiber has greater strength than a natural fiber. The fibers of thread can be staple length fibers or filament fibers. A filament fiber is a continuous fiber and can be very long. Silk is one continuous filament fiber. Synthetic fibers are produced as continuous filaments then cut into desired staple lengths.
Staple fibers are fairly short, usually up to two inches in length.
Cotton is an example of a staple fiber. Synthetic filament fibers are cut into staple fibers of desired length, sometimes up to five inches. Fiber Twist Thread is made by aligning and then twisting fibers together. Thread made from longer fibers, staple or filament, tend to have greater strength than short staple fibers. Short staple fibers are often used in inexpensive threads, causing them to be fuzzier and weaker than when longer staple length fibers are used.