a combining form occurring in loanwords from Greek and Latin, where it meant “eight” (octagon; octastyle), on this model, used in the formation of compound words, and in chemical terms specialized to mean “having eight atoms” (octavalent).

Nearby words

  1. ocs,
  2. oct,
  3. oct-,
  4. oct.,
  5. octa,
  6. octachord,
  7. octad,
  8. octadecanoic acid,
  9. octagon,
  10. octagon house

Also oct-, octo-.

Origin of octa-

< Greek okta-, combining form of oktṓ eight

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for octa

  • The incautious sovereign having assented to this, Octa and Ebusa arrived with forty ships.

  • After this Eosa and the rest that fled, being encouraged by Octa's success, came also, and were admitted to the same favour.

British Dictionary definitions for octa



a variant spelling of okta


combining form

a variant of octo-
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

Word Origin and History for octa


before vowels oct-, word-forming element meaning "eight," from Greek okta-, okt-, from PIE *okto(u) "eight" (see eight). The variant form octo- often appears in words taken from Latin, but the Greek form is said to be the more common in English.

Online Etymology Dictionary, © 2010 Douglas Harper