 The word " amphibian " is derived from the Ancient Greek term ἀμφίβιος ( amphíbios ) , which means " both kinds of life " , ἀμφί meaning " of both kinds " and βιος meaning " life " . The term was initially used as a general adjective for animals that could live on land or in water , including seals and otters . Traditionally , the class Amphibia includes all tetrapod vertebrates that are not amniotes . Amphibia in its widest sense ( sensu lato ) was divided into three subclasses , two of which are extinct : 
