A cetacean is a member of the family of large aquatic mammals such as whales, dolphins, and porpoises. They have flippers for forearms and vestigial hind limbs. A cetacean' has a tail but not hind limbs.
The word cetacean comes from the Latin word cetus, which was used to refer to any large sea creature, and the Greek word ketos, which was a sea monster or whale. The suffix acea means "of the nature of," so cetacean describes a creature belonging to the family of whales or dolphins. As an adjective, the word is used to describe things related to this group. If you like whales and dolphins, you may enjoy cetacean stories like "Moby Dick."
