A fibre is a piece of material which is long, thin and flexible, like a length of thread. Plant fibres are the basis of fabric such as cotton. Silk and wool fibres come from animals. In the 20th century many artificial fibres were invented like nylon and polyester.
There are many uses for fibres. They can be spun together into filaments, thread, string or rope. They can be woven in fabric or in composite materials. They can also be matted into sheets to make products such as paper or felt (as felt hats). Synthetic fibres are the cheapest to make.