- any of several tropical, freshwater fishes of the family Characidae, often kept in aquariums.
- a combining form meaning “four,” used in the formation of compound words: tetrabranchiate.
noun plural -ra or -ras
- any of various brightly coloured tropical freshwater fishes of the genus Hemigrammus and related genera: family Characidae (characins)
word-forming element meaning “four,” from Greek tetra-, combining form of tettares, tessares “four” (see four). pref.
- Composed of or containing four atoms, molecules, or groups:tetrasaccharide.