Ortho-
prefix ·Common ·High school level
Definitions
- 1 Right angle, perpendicular. morpheme
"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. morpheme
"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. morpheme
"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. morpheme
"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. morpheme
"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"
Show 11 more definitions
- 6 Straight in form. morpheme
"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. morpheme
"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-). morpheme
"E.g., orthophenylene, orthosubstitution, orthocleavage."
- 9 Having an extra proportion of water. morpheme
"E.g., orthophosphate, orthosilicate, orthoferrite."
- 10 Independent, separate. morpheme
"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. morpheme
"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. morpheme
"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. morpheme
"E.g., orthopositronium, orthohelium, orthoquarkonium."
- 14 Orthopaedics. morpheme
"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. morpheme
"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. morpheme
"E.g., orthogneiss is a gneiss derived from igneous, rather than sedimentary (paragneiss); orthoamphibolite, orthocumulate."
Example
More examples"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."
Etymology
Learned borrowing from Ancient Greek ὀρθός (orthós).
Related phrases
More for "ortho-"
Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.