tetra
noun
any of several tropical, freshwater fishes of the family Characidae, often kept in aquariums.
tetra
1 American
[te-truh]
/ ˈtɛ trə /
noun
-
tetras
plural
tetra-
2
American
tetra
1
British
/ ˈtɛtrə /
noun
tetra-
2
British
combining form
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.
Other Word Forms
Noun Inflected Forms
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
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
Cavefish are cousins of the Mexican tetra river fish that flooded into underground caves over 100,000 years ago.
From Science Daily ● Mar. 18, 2024
When floods carried some Mexican tetra river fish, Astyanax mexicanus, into about 30 different caves, other fish of the same species remained at the surface, providing a natural study in contrasting evolutionary paths.
From Washington Post ● Feb. 2, 2023
Another keystone species is the banded tetra, a fish in tropical streams, which supplies nearly all of the phosphorus, a necessary inorganic nutrient, to the rest of the community.
From Textbooks ● Sep. 6, 2018
I will not only go to New York and hang out behind the counter and mess with people, but “The Original Soup Man” is now in supermarkets in tetra pack cartons.
From Washington Times ● Jan. 11, 2017
A thousand neon tetra, a flock of living quicksilver sewing needles, turned 90 degrees in perfect unison, then did it again, and again, and again, describing a neat, angular box in the water.
From Home Again, Home Again by Cory Doctorow
O, usually divalent, but tetravalent and possibly hexavalent in oxonium and other salts; S, Se, Te, di-, tetra- and hexa-valent; Cr, di-, tri- and hexa-valent; Mo, W, di-, tri-, tetra-, penta- and hexa-valent.
From Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" by Various
The number of NO3 groups which unite with the cellulose molecule under these conditions depends upon the temperature, pressure, etc., employed during the nitration process; di-, tri-, tetra-, penta-, and hexanitrates are all known.
From The Chemistry of Plant Life by Roscoe Wilfred Thatcher
B, trivalent; Al, trivalent, but possibly also tetra- or penta-valent; Ga, divalent and trivalent; In, mono-, di- and tri-valent; Tl, monovalent and trivalent.
From Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" by Various
This group spans more than 10,000 species, from catfish to aquarium favorites such as tetras and zebrafish.
From Science Daily ● Nov. 3, 2025
I didn’t see the usual darting of neon tetras, and the guppy tanks were all dark.
From "Please Ignore Vera Dietz" by A.S. King
Pencroff had found in the grass half-a-dozen tetras nests, with two or three eggs in each.
From The Mysterious Island by Stephen W. White
Herbert held his breath with excitement, while Pencroff, with dilated eyes, open month, and lips parted as if to taste a morsel of tetras, scarcely breathed.
From The Mysterious Island by Stephen W. White
Even the couroucous were invisible, and it seemed likely that the sailor would be obliged to return to that swampy place where he had fished for tetras with such good luck.
From The Mysterious Island by Stephen W. White
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
