ortho

¹

[ awr-thoh ]

adjective

, Chemistry.

1. pertaining to or occupying two adjacent positions in the benzene ring. Compare meta ³, para ³.

ortho-

²

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 (H 3 BO 3 ) and potassium orthoborate (K 3 BO 3 )); if the acid ends in -ous, the corresponding salt ends in -ite ( orthoantimonous acid (H 3 SbO 3 ) and potassium orthoantimonite (K 3 SbO 3 )).

ortho-

combining_form

1. straight or upright

   orthotropous

2. perpendicular or at right angles

   orthoclastic

3. correct or right

   orthodox

   orthodontics

   orthoptics

   orthography

4. often in italics denoting an organic compound containing a benzene ring with substituents attached to adjacent carbon atoms (the 1,2- positions) o- Compare oarsman Compare oarsman

   orthodinitrobenzene

5. denoting an oxyacid regarded as the highest hydrated form of the anhydride or a salt of such an acid See meta-

   orthophosphoric acid

6. denoting a diatomic substance in which the spins of the two atoms are parallel See para- 1

   orthohydrogen

Word History and Origins

Origin of ortho¹

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

Origin of ortho²

< Greek, combining form of orthós straight, upright, correct

Word History and Origins

Origin of ortho¹

from Greek orthos straight, right, upright

Example Sentences

This process poses challenges including selective addition of bromine at the ortho position, difficulty working with certain chemical groups, and the tendency of o-bromobenzenethiols to oxidize easily in air releasing unpleasant odors.

From Science Daily

Under normal conditions, ortho- and para-H2 are present in a 3:1 ratio, with ortho-H2 slightly more energetically unstable than para-H2.

From Science Daily

But by the time police arrived at the LATTC/Ortho Institute Metro station around 3:45 p.m., the victim was gone.

From Los Angeles Times

In 2019, Cargle wrote an anonymous post on a live public document — called Ortho Match — that is regularly checked and updated by medical students applying to orthopedic surgery residencies.

From Los Angeles Times

I also thought about the way a pair of scientifically cushioned Triple-E ortho New Balances would've probably taken some of the pressure off my knees.

From Salon