Tegument is a terminology in helminthology for the name of the outer body covering among members of the phylumPlatyhelminthes. The name is derived from a Latin word tegumentum or tegere, meaning "to cover". It is characteristic of all flatworms including the broad groups of tapeworms and flukes. Once considered to be a non-living component, it is now known to be a dynamic cellular structure. In fact it is a living structure consisting of proteins, lipids, carbohydrates and RNA. It forms the protective layer and the host-parasite interface of the worms, serving both secretory and absorptive functions.