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-o-

1.
the typical ending of the first element of compounds of Greek origin (as -i-, is, in compounds of Latin origin), used regularly in forming new compounds with elements of Greek origin and often used in English as a connective irrespective of etymology:
Franco-Italian; geography; seriocomic; speedometer.
Compare -i-.
Origin
Middle English (< Old French) < Latin < Greek
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for -o-

-o-

connective vowel
1.
used to connect elements in a compound word: chromosome, filmography Compare -i-
Word Origin
from Greek, stem vowel of many nouns and adjectives in combination
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
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-o- in Medicine

-o-
Used as a connective to join word elements: acidophilic.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Difficulty index for -o-

Few English speakers likely know this word

Word Value for -o-

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