The Viperidae (vipers) are a family of venomous snakes found in most parts of the world, excluding Antarctica, Australia, New Zealand, Madagascar, Hawaii, various other isolated islands, and north of the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four subfamilies are currently recognised. They are also known as viperids. The name "viper" is derived from the Latin word, vipera, -ae, which means "viper".