deca-

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-.

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-?

• decadrachm
• decapod (using the equivalent form of deca- in Latin)
• decastyle using the equivalent form of deca- in Greek)
• decastylos using the equivalent form of deca- in Latin)
• decasyllable
• decanormal

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

• dactylo-
• de-
• deci-
• deka-
• dextro-
• dodeca-

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.

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?