|fish (fĭsh) Pronunciation Key
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Plural fish or fishes
Any of numerous cold-blooded vertebrate animals that live in water. Fish have gills for obtaining oxygen, a lateral line for sensing pressure changes in the water, and a vertical tail. Most fish are covered with scales and have limbs in the form of fins. Fish were once classified together as a single group, but are now known to compose numerous evolutionarily distinct classes, including the bony fish, cartilaginous fish, jawless fish, lobe-finned fish, and placoderms.