Are a porpoise and dolphin the same thing?

No, porpoises and dolphins are not the same thing, although they are both members of the same family, the oceanic dolphins (Delphinidae).

Here's what differentiates them:

Porpoises:

* Smaller and stouter than dolphins.

* Have a blunt, spade-shaped head with a small, triangular dorsal fin.

* Teeth are spade-shaped and are not visible when the mouth is closed.

* Generally quieter than dolphins and do not make whistles or clicks as frequently.

Dolphins:

* Larger and more slender than porpoises.

* Have a long, pointed snout and a curved, falcate (crescent-shaped) dorsal fin.

* Teeth are conical and are visible when the mouth is closed.

* Highly vocal and communicate using a variety of whistles, clicks, and other sounds.

However, it can be tricky to tell them apart at a distance.

Key takeaway: Porpoises and dolphins are closely related but have distinct physical characteristics. While they are both considered "dolphins," the term "porpoise" refers to a specific type of dolphin.