A worm is an elongated, soft-bodied invertebrate. Some species of worms are so different from- even unrelated to- each other that they have not been classified under a single group.Distribution and habitatThere are at least 1,000,000 kinds of worms. They are found almost all over the world. Worms are universal in distribution, occurring in marine, freshwater, and terrestrial habitats. Some worms that live in the ground help to condition the soil (e.g., annelids, aschelminths). Many thri