The anatomy of Lampanyctodes hectoris
1. operculum (gill cover) 2 & 5. lateral line 3. dorsal fin 4 fat fin 6. caudal fin 7. anal fin 8. photophores 9. pelvic fins paired 10. pectoral fins (paired)

Tail fins on a Cadillac car

A fin is a surface used to produce lift and thrust or to steer while traveling in water, air, or other fluid media. The word was first used for the limbs of fish, but it is now also used to mean other animal limbs and human-made devices.

The fins of fish are called:

• Dorsal fin on the back. These fins keep the fish from rolling over.
• Caudal or tail fin. This fin pushes the fish forward in the water.
• Pectoral fins (paired). These fins help the fish steer.
• Pelvic fins (paired). These fins help the fish steer.
• Anal fin: stability