Blenny is a common name for a type of fish. The term is ambiguous, having been applied to several families of percomorph marine, brackish, and some freshwater fish sharing similar morphology and behaviour. Six families are considered "true blennies", all grouped together under the order Blenniiformes; its members are referred to as blenniiformids. About 151 genera and nearly 900 species have been described within the order. The order was formerly classified as a suborder of the Perciformes but the 5th Edition of Fishes of the World divided the Perciformes into a number of new orders and the Blenniiformes were placed in the percomorph clade Ovalentaria alongside the such taxa as Cichliformes, Mugiliformes and Gobiesociformes.