Collins English-English Dictionary

ortho-

1. 1. combining form [often in italics] denoting an organic compound containing a benzene ring with substituents attached to adjacent carbon atoms (the 1,2- positions) o- - Compare para- meta-

   orthodinitrobenzene

2. 2. combining form straight or upright

   orthotropous

3. 3. combining form perpendicular or at right angles

   orthoclastic

4. 4. combining form correct or right

   orthodontics

   orthodox

   orthography

   orthoptics

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

   orthophosphoric acid

6. 6. combining form denoting a diatomic substance in which the spins of the two atoms are parallel - Compare para-

   orthohydrogen

7. 7. combining form [Etymology] from Greek orthos straight, right, upright