tetra

noun

1. any of several tropical, freshwater fishes of the family Characidae, often kept in aquariums.

1. a combining form meaning “four,” used in the formation of compound words: tetrabranchiate.

noun plural -ra or -ras

1. any of various brightly coloured tropical freshwater fishes of the genus Hemigrammus and related genera: family Characidae (characins)

combining form

1. fourtetrameter

word-forming element meaning “four,” from Greek tetra-, combining form of tettares, tessares “four” (see four). pref.

1. Four:tetradactyl.
2. Composed of or containing four atoms, molecules, or groups:tetrasaccharide.