Fish (plural: fish or fishes) are a group of animals with bones which live in water and respire (get oxygen) from their gills.
Fish used to be a class of vertebrates. Now the term covers five classes of animals that live in the water:
There are more fish than four-limbed animals: there are over 33,000 described species of fish. Fish are usually covered with scales. They have two sets of paired fins and several unpaired fins. Most fish are cold-blooded (poikilotherm).