Dictionary.com
definitions
  • synonyms

ortho

[awr-thoh]
See more synonyms for ortho on Thesaurus.com
adjective Chemistry.
  1. pertaining to or occupying two adjacent positions in the benzene ring.Compare meta2, para3.
Show More

Origin of ortho

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

ortho-

  1. 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).
  2. 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)).
Show More
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. 2018

Examples from the Web for ortho

Contemporary Examples

Historical Examples

British Dictionary definitions for ortho

ortho-

before a vowel orth-

combining form
  1. straight or uprightorthotropous
  2. perpendicular or at right anglesorthoclastic
  3. correct or rightorthodontics; orthodox; orthography; orthoptics
  4. (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
  5. denoting an oxyacid regarded as the highest hydrated form of the anhydride or a salt of such an acidorthophosphoric acid See meta- (def. 6)
  6. denoting a diatomic substance in which the spins of the two atoms are parallelorthohydrogen See para- 1 (def. 8)
Show More

Word Origin

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

Word Origin and History for ortho

ortho-

before vowels orth-, word-forming element meaning "straight, upright, rectangular, regular; true, correct, proper," now mostly in scientific and technical compounds, from Greek ortho-, stem of orthos "straight, true, correct, regular," from PIE *eredh- "high" (cf. Sanskrit urdhvah "high, lofty, steep," Latin arduus "high, steep," Old Irish ard "high").

Show More
Online Etymology Dictionary, © 2010 Douglas Harper
ortho in Medicine

ortho-

pref.
  1. Straight; upright; vertical:orthotropic.
  2. Correct; correction:orthopsychiatry.
  3. Hydrated form of an acid or of its salts:orthoboric acid.
  4. Diatomic molecules in which the nuclei have the same direction of spin:orthohydrogen.
  5. Of or relating to one of three possible isomers of a benzene ring with adjacent carbon atoms having attached chemical groups:ortho-dibromobenzene.
Show More
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.