octo-

American  

1. variant of octa-.

   octosyllabic.

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octo- British  

combining form

1. eight

   octosyllabic

   octagon

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Usage

What does octo- mean? Octo- is a combining form used like a prefix meaning “eight.” It is used in a great many scientific and technical terms. Octo- comes from te Greek oktṓ, meaning “eight.” The Latin equivalent, which is almost identical in spelling and pronunciation, is octō. What are variants of octo-?When combined with words or word elements that begin with a vowel, octo- becomes oct-, as in octane. Another variant of octo- is octa-, as in octastyle. Want to know more? Check out our Words That Use entries for both oct- and octa-.

Etymology

Origin of octo-

from Latin octo, Greek okto

Example Sentences

If you’re a septua-, octo- or nonagenarian by Spotify’s accounting, you may find yourself in hip company.

From The Wall Street Journal • Dec. 4, 2025

I joke that we live in a blue-zone, at least for women, because we have so many healthy, active, vibrant female octo- and nonagenarians.

From Salon • Jan. 4, 2024

His decision to abdicate saved the church from one messy situation — being governed by a weakened octo- or nonagenarian.

From Washington Post • Jul. 8, 2021