tetra

noun

Etymology: From translingual Tetragonopterus, an obsolete genus that included these fish, ultimately from Ancient Greek τετράγωνος (tetrágōnos, “square, quadrilateral”) + πτερόν (pterón, “wing, fin”).

1. Any of numerous species of small freshwater fish of the South American family Characidae and West African family Alestidae, popular in home aquariums.

   “Among them were ancient relatives of the piranhas and those popular aquarium fish the tetras, along with garfish and freshwater coelacanths, known as mawsonids.”