Standard Lemma guide

ortho-

prefix · 16 senses · updated from the 2026-07-25 local source snapshot

Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.

Sound

Pronunciation

Each Play button uses your device's default local English voice, or a natural local fallback. The selected voice name appears after playback. This is synthesized speech, not a source recording.

  • Received-Pronunciation: /ɔː.θə-/
  • Received-Pronunciation: /ɔːˈθɒ-/
  • General-American: /oɹ.θə-/
  • General-American: /oɹˈθɑ-/
  • US: Recorded audio is listed in the source snapshot.

1

prefix

Meaning 1

Right angle, perpendicular.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

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.

Meaning relationships

Synonyms: cross-

Antonyms: none provided

2

prefix

Meaning 2

Proper, righteous, pure.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Examples

  • 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.

Meaning relationships

Synonyms: eu-

Antonyms: none provided

3

prefix

Meaning 3

To correct or fix.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Examples

  • 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.

Meaning relationships

Synonyms: fix-

Antonyms: none provided

4

prefix

Meaning 4

Same, from the same.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Examples

  • 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.

Meaning relationships

Synonyms: ipsi-

Antonyms: none provided

5

prefix

Meaning 5

Normal, ordinary.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Examples

  • 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

Meaning relationships

Synonyms: normo-

Antonyms: none provided

6

prefix

Meaning 6

Straight in form.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Examples

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

Meaning relationships

Synonyms: recti-

Antonyms: none provided

7

prefix

Meaning 7

Orthorhombic crystal structure.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Topics: chemistry, crystallography, natural-sciences, physical-sciences

Examples

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

Meaning relationships

Synonyms: none provided

Antonyms: none provided

8

prefix

Meaning 8

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

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Topics: chemistry, natural-sciences, organic-chemistry, physical-sciences

Examples

  • E.g., orthophenylene, orthosubstitution, orthocleavage.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

9

prefix

Meaning 9

Having an extra proportion of water.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Topics: chemistry, natural-sciences, physical-sciences

Examples

  • E.g., orthophosphate, orthosilicate, orthoferrite.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

10

prefix

Meaning 10

Independent, separate.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Examples

  • 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.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

11

prefix

Meaning 11

Original, primary.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Examples

  • 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.

Meaning relationships

Synonyms: proto-

Antonyms: none provided

12

prefix

Meaning 12

Parallel lines or columns.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Examples

  • 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.

Meaning relationships

Synonyms: para-

Antonyms: none provided

13

prefix

Meaning 13

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

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Topics: natural-sciences, physical-sciences, physics

Examples

  • E.g., orthopositronium, orthohelium, orthoquarkonium.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

14

prefix

Meaning 14

Orthopaedics.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Topics: medicine, sciences

Examples

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

Meaning relationships

Synonyms: none provided

Antonyms: none provided

15

prefix

Meaning 15

Vertical or upright in movement.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Examples

  • 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.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

16

prefix

Meaning 16

Igneous.

Definition source: English Wiktionary via Wiktextract

Usage: morpheme

Topics: geography, geology, natural-sciences

Examples

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

Meaning relationships

Synonyms: igneo-

Antonyms: none provided

History

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).