Dorsal means relating to the back or upper side of an animal or body part. When a marine biologist describes a dolphin's dorsal fin, she's talking about the fin on its back that cuts through the water's surface. When scientists study the dorsal side of a beetle, they're examining its top surface, not its belly.

The word appears frequently in biology and medicine. A shark's most recognizable feature is its tall dorsal fin. Birds have dorsal feathers covering their backs. In human anatomy, doctors might refer to the dorsal surface of your hand (the side with knuckles, not your palm) or the dorsal side of your tongue.

The opposite of dorsal is ventral, which refers to the belly or underside. Think of it this way: if you were swimming like a fish, your dorsal side would face the sky while your ventral side would face the ocean floor. Understanding dorsal helps you follow nature documentaries, read science articles, and know exactly which part of an animal someone means when they describe its features.