A fiber is a small short piece of hair. A filament is a long strand of a single substance. In textile yarn, individual fibers or filaments are wound together to make threads. Textile yarn can be made with natural fibers from substances such as wool from sheep, silk from silkworms, or cotton and linen from plants. Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery, or rope making.