Porpoises are related to whales and dolphins, and there are some differences between a dolphin and a porpoise.
Porpoises are slightly smaller than dolphins for one.
Also, dolphins have a sharp snout and cone-shaped teeth, while porpoises have a rounded snout and spade-shaped teeth.
Both dolphins and porpoises are predators of fish, squid, and crustaceans, and are descendants of land-living hoofed animals, or ungulates that first entered the oceans around 50 million years ago.
The differences between dolphins and porpoises are so small that it almost makes us wonder if the people in charge of delineating species have a little too much time on their hands.