In some cases, scientists use the term whale to describe all animals in the order Cetacea. This includes large species such as humpback and blue whales, as well as smaller species, such as the bottle-nosed dolphin. Most of the time, people use the term "whale" only to describe the larger whale species, and refer to smaller cetaceans as dolphins or porpoises.
Dolphins, which make up the family Delphinidae, are toothed whales characterized by their relatively small size, bulbous head and beaked snout. Orcas and pilot whales are also included in this family, though they are much larger and their beak is less pronounced. Porpoises, members of the family Phocaenidae, are small toothed whales that have a rounded head rather than a beaked snout.
In the next section, we'll explore the history of whale hunting and conservation to see how the relationship between whales and people has evolved over the years.