Dolphins belong to a group of marine mammals called toothed whales. The word dolphin comes from the Greek delphis, which means dolphin. The toothed whale group, or Odontoceti, includes not only dolphins but also porpoises, river dolphins, and even sperm whales. The dolphin family, Delphinidae, which is part of the toothed whale group, includes dolphins such as the bottlenose, spinner, and spotted dolphins as well as the killer whale, pilot whale, and false killer whale.
Dolphins are mammals just like humans and have the same basic mammal traits: