An appendage of fish and fish-like aquatic animals used for locomotion, steering, and balancing of the body. The skin fold forming the fin membrane is supported by cartilaginous, horny, or bony fin rays, which can be soft and flexible (soft rays) or hard and inflexible (fin spines). The median unpaired fins of fish include the dorsal fin on the back, the caudal fin (tail fin), and the anal fin behind the vent (anus). Usually there are also two pairs of lateral fins: the pectoral fins and the pelvic (also called ventral or abdominal) fins. See also appendicular skeleton.
Subjects: Zoology and Animal Sciences.