Fiber is a rope or string used as a component of composite materials, or, when matted into sheets, used to make products such as paper, papyrus, or felt.

Natural fibers used in textile manufacture include, cotton, flax, hemp, and wool.

Fibers are often used in the manufacture of other materials.

The strongest engineering materials often incorporate fibers, for example carbon fiber and Ultra-high-molecular-weight polyethylene.

Synthetic fibers can often be produced very cheaply and in large amounts compared to natural fibers, but for clothing natural fibers can have certain advantages over their synthetic counterparts.