fin (redirected from tail fin)

fin, organ of locomotion characteristic of fish and consisting of thin tissue supported by cartilaginous or bony rays. In some fish, e.g., the eel, a single fin extends from the back, around the tail, and along the ventral surface. In the majority of fishes, however, there are one, two, or three dorsal fins, a distinct tail fin, and an anal fin. These are called median, or unpaired, fins. In addition to these unpaired fins, most fish also have paired fins. These are the pectoral fins, placed just back of the gills, and the pelvic, or ventral, fins, variable in position and sometimes lacking entirely. The tail is an important organ of locomotion and the paired fins are used for steering, checking speed, balancing, and for slow movements. An adipose fin (fatty tissue without support) is found behind the dorsal fin in some fish, e.g., the salmon and the catfish. See climbing perch; flying fish.

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fin

1. any of the firm appendages that are the organs of locomotion and balance in fishes and some other aquatic animals. Most fishes have paired and unpaired fins, the former corresponding to the limbs of higher vertebrates

2. 

a. Brit a vertical surface to which the rudder is attached, usually placed at the rear of an aeroplane to give stability about the vertical axis

b. a tail surface fixed to a rocket or missile to give stability

3. Nautical a fixed or adjustable blade projecting under water from the hull of a vessel to give it stability or control

4. a projecting rib to dissipate heat from the surface of an engine cylinder, motor casing, or radiator

5. another name for flipper