Fiber is elongated stringy natural, man-made or manufactured material.For natural fibers, generally consist of cellulose, for example cotton, linen, and hemp. Besides, natural animal fibers include spider silk, sinew, hair, and wool.
Man-made fibers are those that are made artificially, but from natural raw materials (often cellulosic). Examples include fiberglass, rayon, acetate, cupro and the more recently developed Lyocell. Synthetic fibers include nylon, acrylic, polyester and graphite fiber.
Yarn is an assemblage of fibers that is laid or twisted together to form a continuous strand , suitable for use in the production of textiles, sewing, knitting, weaving and ropemaking. Yarn can be made from any number of synthetic or natural fibers. Yarns are made up of any number of plys, each ply being a single thread these threads being twisted (plied) together to make the final yarn.
Single yarn - made from a group of filaments or staple fibers twisted together; if untwisted, it will separate into the individual fibers.
Ply yarn - two or more single yarns are twisted together to make a single yarn; if untwisted, it will separate into the single yarns which will separate into individual fibers.