S: (n) fish (any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills) "the shark is a large fish"; "in the living room there was a tank of colorful fish"
S: (n) vertebrate, craniate (animals having a bony or cartilaginous skeleton with a segmented spinal column and a large brain enclosed in a skull or cranium)
S: (n) chordate (any animal of the phylum Chordata having a notochord or spinal column)