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ortho

[ awr-thoh ]
/ ˈɔr θoʊ /
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Definition of ortho

adjective Chemistry.
pertaining to or occupying two adjacent positions in the benzene ring.Compare meta3, para3.
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Origin of ortho

First recorded in 1875–80; independent use of ortho-

Other definitions for ortho (2 of 2)

ortho-

a combining form occurring in loanwords from Greek, where it meant “straight,” “upright,” “right,” “correct” (orthodox) and on this model used in the formation of compound words (orthopedic).
Chemistry.
  1. a combining form used in the name of that acid in a given series of acids that contains the most water (orthoboric acid).Compare meta-, pyro-.
  2. a combining form used in the names of the salts of these acids: if the acid ends in -ic, the corresponding salt ends in -ate (orthoboric acid (H3BO3) and potassium orthoborate (K3BO3)); if the acid ends in -ous, the corresponding salt ends in -ite (orthoantimonous acid (H3SbO3) and potassium orthoantimonite (K3SbO3)).
Also especially before a vowel, orth-.

Origin of ortho-

<Greek, combining form of orthós straight, upright, correct
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use ortho in a sentence

British Dictionary definitions for ortho

ortho-

before a vowel orth-


combining form
straight or uprightorthotropous
perpendicular or at right anglesorthoclastic
correct or rightorthodontics; orthodox; orthography; orthoptics
(often in italics) denoting an organic compound containing a benzene ring with substituents attached to adjacent carbon atoms (the 1,2- positions)orthodinitrobenzene Abbreviation: o- Compare oarsman Compare oarsman
denoting an oxyacid regarded as the highest hydrated form of the anhydride or a salt of such an acidorthophosphoric acid See meta- (def. 6)
denoting a diatomic substance in which the spins of the two atoms are parallelorthohydrogen See para- 1 (def. 8)

Word Origin for ortho-

from Greek orthos straight, right, upright
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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