About This Word Fish, appearing especially in the phrase fresh fish, is prison slang for new, first-time inmates, usually considered naive and vulnerable. Fish, often appearing in the form of fishy or the phrase serving fish, is also slang in drag culture for a very feminine drag queen.

Fish are aquatic vertebrate animals that have gills but lack limbs with digits, like fingers or toes. Recall that vertebrates are animals with internal backbones. Most fish are streamlined in their general body form. The word fish is the same whether it is singular or plural—you can talk about one fish or ten fish.

There are approximately 28,000 species of fish, classified into five classes: hagfish, lampreys, cartilaginous fish, ray-finned fish, and lobe-finned fish. Hagfish are primitive fish with no scales or fins, while lampreys lack scales but have fins and a partial backbone.

fish, any of approximately 34,000 species of vertebrate animals (phylum Chordata) found in the fresh and salt waters of the world. Living species range from the primitive jawless lampreys and hagfishes through the cartilaginous sharks, skates, and rays to the abundant and diverse bony fishes.