A roundworm is a worm that lives inside an animal, and sometimes inside a person. It is a parasite: it stays in the body and takes food there, most often in the gut. It is called round because it is like a thin tube — if you could cut across it, the cut would look like a little circle, not a flat ribbon. That is the real difference from tapeworms, which are flat. People and pets pick them up from dirty hands, from food or water that was not clean, or from soil in some places. Doctors give medicine to kill them; farmers watch for them in dogs, pigs, and horses too. The word is ordinary English for this kind of worm. In a biology class you may hear a longer scientific name, but you do not need it to understand the idea. Though actually, the brown worms in garden soil are a different family of animals — they help plants, and they are not trying to live in you.

蛔蟲（體內寄生的圓形蠕蟲；生物課較廣的名稱是線蟲）