| ortho- or (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. | (often in italics) Compare meta- Compare para- o- denoting an organic compound containing a benzene ring with substituents attached to adjacent carbon atoms (the 1,2- positions): orthodinitrobenzene |
| 5. | See meta- denoting an oxyacid regarded as the highest hydrated form of the anhydride or a salt of such an acid: orthophosphoric acid |
| 6. | See para- denoting a diatomic substance in which the spins of the two atoms are parallel: orthohydrogen |
| [from Greek orthos straight, right, upright] | |
| orth- or (before a vowel) orth- | |
| —combining form | |
| [from Greek orthos straight, right, upright] | |
| a printed punctuation mark (‽), available only in some typefaces, designed to combine the question mark (?) and the exclamation point (!), indicating a mixture of query and interjection, as after a rhetorical question. |
| a fool or simpleton; ninny. |