Dolphins are a number of kinds of small odontoceti, or toothed whales.
The term porpoise, sometimes used synonymously with dolphin, in fact should refer only to certain small blunt-snouted and spade-toothed types, generally of inshore habitat, such as the harbour porpoise of the North Atlantic.
In addition to the many types of sea-dwelling dolphin, river dolphins are found in certain of the world's great rivers.
Dolphins mainly feed upon small fish and squid.
Dolphins typically live in small family groups. They are highly sociable, and if left alone will freely associate with other species of whale, and with humans. Human interaction includes accompanying ships and mingling with swimmers. There have been a number of historic cases of dolphins assisting human fishermen. Dolphins generally avoid SCUBA divers, however, because they dislike the noise made by their regulators.
Dolphins are commonly found in company with tuna, and are frequently netted with them.
Dolphins are highly intelligent, and captive dolphins have been trained to perform complex acts at aquariums, and to carry out military minelaying and guard duties.
Dolphins live in salt water but can survive in fresh water.
The largest species dolphin is the orca (or "killer whale").
Dolphins, along with all other water-dwelling animals, were created by God on the fifth day of Creation.