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• tetra
  tetra

  noun

  any of several tropical, freshwater fishes of the family Characidae, often kept in aquariums.
• tetra-
  tetra-

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

tetra

¹ American  

[te-truh] / ˈtɛ trə /

noun

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

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tetra- ² American  

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

   tetrabranchiate.

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tetra ¹ British  

/ ˈtɛtrə /

noun

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

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tetra- ² British  

combining form

1. four

   tetrameter

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Usage

What does tetra- mean? Tetra- is a combining form used like a prefix meaning “four.” It is used in a great many scientific and other technical terms. In chemistry, tetra- is specifically used to indicate four atoms or four groups of atoms in compounds, e.g., tetrachloride. Tetra- ultimately comes from the Greek téttares, meaning “four.” The name of the classic video game Tetris is based in part on this Greek root. Find out the rest of the story of how Tetris got its name here. The Latin word for “four” is quattor, source of the combining forms quadr-, quadra-, quadri-, and quadru-. Learn about their specific applications in our Words That Use articles for the forms. What are variants of tetra-?When combined with words or word elements that begin with a vowel, tetra- becomes tetr-, as in tetracid.

Etymology

Origin of tetra¹

1930–35; shortening of New Latin Tetragonopterus former genus name. See tetragon, -o-, -pterous

Origin of tetra-²

< Greek, combining form of téttara, neuter of téttares four

Example Sentences

The New York-based company’s Tetra Paks—four-sided paperboard cartons emblazoned with palm trees—lead the coconut water pack, dominating the U.S. market with a 44% market share.

From Barron's • Nov. 13, 2025

Tetra Tech and the Vietnamese construction firm did not respond to questions for this story.

From Salon • Mar. 19, 2025

Tetra Tech focuses on water, environment and sustainable infrastructure and a substantial chunk of its revenue comes from contracts with federal, state and local government agencies.

From Los Angeles Times • Mar. 18, 2025

Some assessments emailed by Tetra Tech were lost in the spam folders of school administrators or faced several weeks or months of delays getting the state’s review and approval.

From Seattle Times • Jan. 26, 2024

Talis uti fama est, vasta Franciscus eremo Tetra vagabatur solus per lustra ferarum, Sylvestrique tulit genti pia verba salutis Impius, atque lupos domuit, Lybicosque leones.

From Poemata : Latin, Greek and Italian Poems by John Milton by Cowper, William