Cotton
Cotton is a plant fiber that produces heavy, smooth, breathable knitted fabric without wool's natural elasticity, well suited to summer garments.
Explanation
Cotton yarn is made from the plant fiber of the cotton plant, and differs from animal fibers like wool by being heavier, less elastic, and without natural moisture insulation. This makes cotton well suited to summer garments, dishcloths, and other items that need to breathe and withstand frequent washing, but cotton gauge swatches should hang for a while before measuring, since cotton often 'grows' longer under its own weight. Mercerization treatment gives cotton yarn extra sheen and strength.