ortho-

ortho- or orth-

pref.

1. Straight; upright; vertical: orthotropous.

2. Perpendicular: orthorhombic.

3. Correct; correction: orthopsychiatry.

4. The most fully hydrated form of an acid or of its salts: orthoboric acid.

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

6. Of or relating to one of three possible isomers of a benzene ring with two attached chemical groups in which the carbon atoms with attached groups are adjacent: ortho-dibromobenzene.

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[Middle English, from Old French, from Latin, from Greek, from orthos, straight, correct, right.]

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ortho- before a vowel, orth-

combining form

1. straight or upright orthotropous

2. perpendicular or at right angles orthoclastic

3. correct or right orthodontics orthodox orthography orthoptics

4. (Chemistry) (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 para-¹ [6] meta- [4]

5. (Chemistry) denoting an oxyacid regarded as the highest hydrated form of the anhydride or a salt of such an acid orthophosphoric acid Compare meta- [6]

6. (Chemistry) denoting a diatomic substance in which the spins of the two atoms are parallel orthohydrogen Compare para-¹ [8]

[from Greek orthos straight, right, upright]