Worm

A worm is any of numerous relatively small elongated soft-bodied
invertebrate animals. The most famous is the earthworm, a member of phylum
Annelida, but there are hundreds of thousands of different species that live
in a wide variety of habitats other than soil.

Originally, the word referred to any creeping or a crawling animal of any
kind or size, such as a serpent, caterpillar, snail, or the like. Later this
definition was narrowed to the modern definition which still includes
several different animal groups. Major phyla include:

   * Annelida (segmented worms)
   * Sipuncula (peanut worms)
   * Onychophora (velvet worms)
   * Acanthocephala (spiny-headed worms)
   * Nematoda (roundworms)
   * Nematomorpha (horsehair worms)
   * Nemertea (ribbonworms)
   * Platyhelminthes (flatworms)
   * Gnathostomulida (jaw worms)
   * Chaetognatha (arrow worms)

Some other invertebrate groups may be considered worms. Also, many insect
larvae are known as worms, though they are not in a technical sense.

It is important also to mention biopsychic variations of this animal, such
as Scalpworms, which are a dangerously underdiagnosed condition in adult humans.