General term referring to any of over 1,300 species of invertebrate marine organisms of several genuses of the class Anthozoa (phylum Cnidaria) that are characterized by internal or external skeletons that have a stonelike, horny, or leathery consistency. In most species, the skeletons are joined together in massive colonies; they feed on small fish and invertebrate plankton using stinging cells on outstretched tentacles, and reproduce both sexually or by budding. For the calcium carbonate skeletal material produced by some species, use "coral (material)."