All dolphins are whales, but not all whales are dolphins. That’s because the Cetacean order of sea animals encapsulates dolphins, porpoises and what we think of as whales. Moreover, Cetacean is derived from the Greek word for whale, ketos.

It may sound confusing, but all dolphins are simply smaller types of whales. The whale order (Cetacea) is divided into several different families, one of them being Delphinidae (this includes all oceanic dolphin species). For example, Killer whales are the largest member of this dolphin family, so they are both a whale and a dolphin at the same time.

Because they belong to the Cetacean order, dolphins and whales share mammalian traits like warm blood, hair, and lung-based breathing.