[ te-truh ]
/ ˈtɛ trə /
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any of several tropical, freshwater fishes of the family Characidae, often kept in aquariums.
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Origin of tetra

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

Other definitions for tetra (2 of 2)


a combining form meaning “four,” used in the formation of compound words:tetrabranchiate.
Also especially before a vowel, tetr-.

Origin of tetra-

<Greek, combining form of téttara, neuter of téttaresfour
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


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.

Examples of tetra-

One example of a word you may have encountered that features tetra- is tetragon, “a polygon having four angles or sides,” such as a square or rectangle. A tetragon is also known as a quadrangle or quadrilateral.

The first part of the word, tetra-, means “four,” as we know. The -gon portion of the word may also look familiar: it is a combining form meaning “angled” or “angular,” from the Greek gōnía. Tetragon literally translates to “four-angled.”

The word tetragon comes from the Greek tetrágōnon, which uses the equivalent form of tetra- in the language.

Another geometric shape using the combining form tetra- is tetrahedron, a triangular pyramid; it’s so named because the shape is formed using four (tetra-) faces (-hedron).

You may have also heard of a tetralogy, which refers to a series of four related plays, novels, films, video games, or other media. It’s like a trilogy—plus one. Shakespeare’s so-called Henriad is an example of a tetralogy. It consists of four connected history plays: Richard II, Henry IV, Part 1, Henry IV, Part 2, and Henry V.

What are some words that use the combining form tetra-?

Many of the following words use the equivalent form of tetra- in Greek. 

What are some other forms that tetra- may be commonly confused with?

Break it down!

The combining form -dactyl means “possessing fingers or toes” of the kind specified by the first part of the word. A tetradactyl is an animal with how many toes?

How to use tetra in a sentence

British Dictionary definitions for tetra (1 of 2)

/ (ˈtɛtrə) /

noun plural -ra or -ras
any of various brightly coloured tropical freshwater fishes of the genus Hemigrammus and related genera: family Characidae (characins)

Word Origin for tetra

C20: short for New Latin tetragonopterus (former genus name), from tetragon + -o- + -pterous, from Greek pteron wing

British Dictionary definitions for tetra (2 of 2)


before a vowel tetr-

combining form

Word Origin for tetra-

from Greek
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012