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a combining form meaning “ten,” used in the formation of compound words: decapod.
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Also especially before a vowel, dec-.
Compare deci-, deka-.

Origin of deca-

<Greek deka-, combining form of dékaten; cognate with Latin decem
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


What does deca- mean?

Deca- is a combining form used like a prefix meaning “ten.” It is used occasionally in technical and scientific terms.

Deca- comes from Greek déka, meaning “ten.” A related Latin-origin form is deci-, from Latin decimus, “tenth.” Want to learn more? Check out our Words That Use entry for deci-.

Despite the similarity between the two forms, it’s important not to confuse deca-, meaning “ten,” with deci-, which means “tenth.” A decagram is ten grams (10 g), but a decigram is one-tenth of a gram (0.1 g).

What are variants of deca-?

When combined with words or word elements that begin with a vowel, deca- becomes dec-, as in decathlon. A related prefix is deka-, which is reserved for the naming of metric units.

Want to know more? Check out our Words That Use articles for dec- and deka-.

Examples of deca-

An example of a term that features deca- is decagon, “a polygon having ten angles and ten sides.” Decagon comes from Medieval Latin decagōnum, which features the equivalent of the form deca-.

We know deca- means “ten,” while the -gon portion of the word, from Greek gōnía, means “angled, angular.” Decagon literally translates to “ten angles.”

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

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

Not every word that begins with the letters deca-, such as decadence or decapitate, is necessarily using the combining form deca- to denote “ten.” Learn why decadence is related to “decay” at our entry for the word.

Break it down!

The combining form -pod means “(one having a kind of) foot.” With this in mind, why are crustaceans such as crabs, lobsters, and crayfish known as decapods?

How to use deca- in a sentence

British Dictionary definitions for deca-


deka-, before a vowel dec- or dek-

denoting ten: decagon . In conjunction with scientific units the symbol da is used

Word Origin for deca-

from Greek deka
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

Scientific definitions for deca-


A prefix that means “ten,” as in decahedron, a polygon having ten faces.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.