Whale, any of the larger species of aquatic mammals belonging to the order Cetacea. The term whale can be used in reference to any cetacean, including porpoises and dolphins, but in general it is applied to those more than 3 metres (10 feet) long. An exception is the 2.7-metre dwarf sperm whale (Kogia simus), so called for its otherwise striking resemblance to its larger namesake. Whales are the heaviest known animals, living or fossil, reaching a maximum size in the blue whale (Balaenoptera musculus) of perhaps more than 30 metres and 200 metric tons (220 short [U.S.] tons)
Whales are distributed throughout the world’s oceans and seas, from the Equator to the polar ice, except for the landlocked Caspian and Aral seas. They are mammals, and they share the defining traits of that group: they breathe air, are warm-blooded, give live birth, suckle their young on milk, and have hair. All are entirely aquatic, with specialized adaptations such as flippers and tail flukes for living in water. Whales must surface regularly to breathe, evacuating their lungs more completely than most mammals in an almost explosive breath known as a blow. Blows are visible because water vapour in the whale’s hot breath condenses when the blow is released.
