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. 2020

Example sentences from the Web for ortho

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
Mr. Tal- mage, true to the fawning, cringing spirit of ortho- doxy, lauds the living queen and cruelly maligns the genius dead.
The Works of Robert G. Ingersoll, Vol. 5 (of 12)|Robert G. Ingersoll
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
This change only occurs when the halogen atom is in the ortho- or para- position to the -N2- group.
Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4|Various

The ortho- and para-nitro-benzoic acids can be obtained by oxidizing ortho-and para-nitro-cinnamic acids.
Encyclopaedia Britannica, 11th Edition, Volume 3, Slice 6|Various
The ortho molecules rotate with odd rotational quantum numbers, while the para molecules rotate with even quantum numbers.
Unwise Child|Gordon Randall Garrett

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

Medical definitions for ortho

ortho-

pref.

Straight; upright; vertical:orthotropic.

Correct; correction:orthopsychiatry.

Hydrated form of an acid or of its salts:orthoboric acid.

Diatomic molecules in which the nuclei have the same direction of spin:orthohydrogen.

Of or relating to one of three possible isomers of a benzene ring with adjacent carbon atoms having attached chemical groups:ortho-dibromobenzene.

MEANINGS

WORD GAMES

LEARN

WRITING

WORD OF THE DAY

ortho

adjective Chemistry.

QUIZZES

CAN YOU GUESS THESE WORDS FROM AROUND THE US?

Origin of ortho

Words nearby ortho

Definition for ortho (2 of 2)