Helminths are parasitic worms. Helminths only include internal parasitic worms. There are trematodes, cestodes, nematodes which each possess different qualities. Helminths have 3 life stages: egg, larval, and adult.
Helminths are eukaryotes. The phylogenetic tree to the left shows the phylum Platyhelmintha in the Lophotrochozoa clade and the phylum Nematozoa in the Ectodysozoa clade. Flatworms are Platyhelminthes and roundworms are Nematozoa.
Below are five examples of helminths which most commonly infect humans.