Nematoda

Nematoda, class of worms known as roundworms. Separate entities within this class are referred to as nematodes. Ranging from microscopic size to over 3 ft (1 m) long, these worms live in soil, water, or in plants or animals as parasites. Hookworms, pinworms, and trichinae are all parasitic nematodes that may live in humans or animals.