ortho-

prefix

Etymology: Etymology tree Proto-Indo-European *h₃erdʰ-der. Proto-Hellenic *ortʰwós Ancient Greek ὀρθός (orthós)lbor. English ortho- Learned borrowing from Ancient Greek ὀρθός (orthós).

1. Right angle, perpendicular.

   “In this sense, it is the angle that is "right" or straight rather than the line; orthogon is a right-angle triangle, orthocentric is a tetrahedron where all three pairs of opposite edges are perpendicular, orthoclastic is a crystal whose cleavage planes are at right angles.”

2. Proper, righteous, pure.

   “E.g., orthorexia is an unhealthy fixation with healthy or righteous eating, an orthotaxon is a true taxon based biological relationships rather than form, orthology is speech which is proper, orthoquartzite is very pure quartz sandstone.”

3. To correct or fix.

   “E.g., orthophotography is the geometrical correction of aerial photographs, orthoptics is the treatment of muscular irregularities of the eye, orthodontics is the correcting of misaligned teeth.”

4. Same, from the same.

   “E.g., An orthocousin, unlike a cross-cousin, is on the same side of the family; orthogamy is when a plant's ovules are fertilized by pollen from the same plant; orthochronous is a transformation which preserves the direction of time.”

5. Normal, ordinary.

   “E.g., orthocclusion is normal occlusion, orthodromic is when neurological impulses are passed in the normal direction, orthogravitropism is the ordinary effect of gravity on plants”

6. Straight in form.

   “E.g., orthoconic is a mollusc shell that is straight rather than spiraled, orthodentin is dentin composed of straight tubes, orthognathous is straight-jawed. .”

7. Orthorhombic crystal structure.

   “E.g., orthochrysotile is an orthorhombic chrysotile, orthopyroxene is a pyroxene that forms orthorhombic crystals, orthohexagonal is having orthorhombic hexagonal symmetry.”

8. In isomeric benzene derivatives, having the two substituents in adjacent (1,2) positions (compare meta- and para-).

   “E.g., orthophenylene, orthosubstitution, orthocleavage.”

9. Having an extra proportion of water.

   “E.g., orthophosphate, orthosilicate, orthoferrite.”

10. Independent, separate.

    “E.g., orthogonal as in statistically independent, orthopair is a pair of disjoint subsets, orthogonal in the sense of two aspects of a software problem are able to be treated separately.”

11. Original, primary.

    “E.g., orthonasal is the first direction from which olfaction happens; orthosteric is the original and unmodulated binding site; orthotone is when a speaker retains the accent.”

12. Parallel lines or columns.

    “E.g., orthostyle is a series of columns in architecture, an ortholinear keyboard has the keys aligned in straight columns, an orthographic projection has its rays parallel.”

13. Of any molecule of the form X₂ in which the two nuclei have parallel spin.

    “E.g., orthopositronium, orthohelium, orthoquarkonium.”

14. Orthopaedics.

    “E.g., orthogeriatrics is the combination of orthopaedics and geriatrics, orthosurgeon is an orthopaedic surgeon, orthoroentgenography is orthopedic roentgenography.”

15. Vertical or upright in movement.

    “E.g., orthotropic is to grow vertically (up or down), orthostasis describes the state of the human body in a standing position, orthograde is walking or standing in that position.”

16. Igneous.

    “E.g., orthogneiss is a gneiss derived from igneous, rather than sedimentary (paragneiss); orthoamphibolite, orthocumulate.”