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-

Words nearby ortho

Ortegal, Ortega Saavedra, Ortega y Gasset, orth-, orthicon, ortho, orthoboric acid, orthocenter, orthocentre, orthocephalic, orthochromatic

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.

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-.
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

Ortho Sol makes precision screws for the most delicate of construction projects: spinal fusion.
Patients Screwed in Spine Surgery ‘Scam’|The Center for Investigative Reporting|November 3, 2014|DAILY BEAST
And also those that contain norgestimate, which include Ortho-Cyclen and Tri-Cyclen.
Birth Control Made My Hair Fall Out, and I’m Not the Only One|Molly Oswaks|October 14, 2014|DAILY BEAST
The influence of position of an alkyl in the aromatic bodies is well shown in ortho-, para- and meta-derivatives.
Poisons: Their Effects and Detection|Alexander Wynter Blyth
The ortho molecules rotate with odd rotational quantum numbers, while the para molecules rotate with even quantum numbers.
Unwise Child|Gordon Randall Garrett

This block is of the ortho-cerite stratum of Drummond Island.
Summary Narrative of an Exploratory Expedition to the Sources of the Mississippi River, in 1820|Henry Rowe Schoolcraft
This substance readily yields ortho-oxybenzoic acid or salicylic acid, which on nitration yields two mononitro-oxybenzoic acids.
Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1|Various
It is well known that di-ortho-substituted benzoic acids are esterified with difficulty.
Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1|Various

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