ortho

¹ American  

[awr-thoh] / ˈɔr θoʊ /

adjective

Chemistry.

1. pertaining to or occupying two adjacent positions in the benzene ring.

---

ortho- ² American  

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 ).

   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 BO3 ) and potassium orthoborate (K 3 BO3 )); if the acid ends in -ous, the corresponding salt ends in -ite (orthoantimonous acid (H 3 SbO3 ) and potassium orthoantimonite (K 3 SbO3 )).

---

ortho- British  

combining form

1. straight or upright

   orthotropous

2. perpendicular or at right angles

   orthoclastic

3. correct or right

   orthodontics

   orthodox

   orthography

   orthoptics

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

---

Etymology

Origin of ortho¹

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

Origin of ortho-²

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

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 • May 23, 2024

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 • Dec. 2, 2022

Drop is offering buy one, get one free on base and ortho kits when you use code MT3BOGOJULY until 11:59PM PT / 2:59AM ET on July 31st.

From The Verge • Jul. 27, 2022

It’s a steel-bodied, five-seat hatchback with front or all-wheel drive, leveraged on the Mazda2 platform, sharing some ortho with the Mazda3 and AWD bits with the compact crossover CX-5.

From The Wall Street Journal • Jan. 27, 2016

The Sunday of my confirmation, I begged my mom to let me take off the ortho boot and put on heels.

From "Courage to Soar" by Simone Biles