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How are dolphins different from porpoises?

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Illustration showing various cetaceans, including baleen whales like the blue whale, fin whale, humpback whale, gray whale, sei whale, northern right whale, and bowhead whale, as well as toothed whales such as the sperm whale, narwhal, beluga, Baird's beaked whale, killer whale, dolphins, and porpoises. Each species is labeled with its scientific name and typical or maximum length, with a size scale in the corner for reference. — cetacean Whales (order Cetacea).

While dolphins and porpoises are both cetaceans and carnivores, they belong to different families and possess distinct physical characteristics.12

The primary differences include:

Body and Snout: Dolphins typically have a more elongated, spindle-shaped body with a pronounced beak-like snout. In contrast, porpoises have a more compact build and a blunt, rounded snout.132
Teeth: Dolphins have cone-shaped teeth, whereas porpoises have teeth that are shaped like a spade (spatulate).12
Dorsal Fin: Most dolphins feature a curved or hooked dorsal fin. Porpoises generally have a smaller, triangle-shaped dorsal fin, though some species, such as the finless porpoise, lack one entirely.12
Size: Porpoises are generally smaller than dolphins, typically reaching a maximum length of about 2 meters (6.6 feet).2

While the term "porpoise" is sometimes colloquially applied to dolphins in North America, scientists reserve the name for the seven species within the family Phocoenidae, which are distinct from the oceanic dolphins of the family Delphinidae.32