prefix
tetra-
Prefix meaning 'four', used in scientific and technical terms such as テトラポッド (tetrapod) or テトラコード (tetrachord).
テトラポッドは海岸の侵食を防ぐために使われる。
Tetrapods are used to prevent coastal erosion.
noun
tetra (fish)
Refers to small tropical freshwater fish of the family Characidae, popular in aquariums.
水槽にネオンテトラを十匹飼っている。
I keep ten neon tetras in the aquarium.