Whales belong to an order of mammals called cetaceans, so an alternative generic term for a whale is a cetacean. However, cetaceans include not only whales, but dolphins and porpoises as well. These mammals are divided into two groups: baleen whales and toothed whales.
The term "whale" is often used to describe the baleen whales, which are generally much larger than toothed whales. The notable exception is the sperm whale, the largest of the toothed whales. Examples of baleen whales include the blue whale, which is the largest animal on Earth, as well as the humpback whale, the sei whale and the right whale.