ortho- /ör-thō- or -tho-/ or sometimes before a vowel orth- /örth-/

1. Denoting: straight
2. Upright
3. Perpendicular
4. Right
5. Genuine
6. Derived from an acid anhydride by combination with the largest number of water molecules (distinguished from meta-; chem)
7. Having substituted atoms or groups attached to two adjacent carbon atoms of the benzene ring (distinguished from meta- and para-, in this sense commonly represented by O-; chem)

orˈtho adjective

A contraction of orthochromatic

An orthochromatic plate

orthoaxˈis noun (pl orthoaxˈes /-akˈsēz/) (crystallography)

The orthodiagonal

orthoboˈrate noun

A salt of orthoboric acid (see boric acid under borax¹)

orthocaine /-kāˈin or -kān/ noun

A white crystalline substance used as a local anaesthetic

orˈthocentre noun

The point of intersection of the altitudes of a triangle

Orthoceras /ör-thosˈə-ras/ noun

(Gr keras horn) a genus of fossil cephalopods with a straight shell

orthochromatˈic adjective

(Gr chrōma colour) of or relating to a photographic emulsion sensitive to some but not all the colours of the visible spectrum (cf panchromatic)

orˈthoclase /-klās or -klāz/ noun

(Gr klasis fracture) common or potash feldspar, monoclinic, with cleavages at right angles

orˈtho-compound noun (chem)

orˈtho-cousin noun

The son or daughter of a father's brother or a mother's sister

orthodiagˈonal noun

(in a monoclinic crystal) that lateral axis which is perpendicular to the vertical axis

orthodontia /-donˈti-ə/ or orthodontˈics noun

(Gr odous, odontos tooth) rectification of crookedness in the teeth

orthodontˈic adjective

orthodontˈically adverb

orthodontˈist noun

orˈthodox adjective

1. (Gr doxa opinion) sound in doctrine
2. Believing, or according to, the received or established doctrines or opinions, esp in religion
3. (with cap) of the Greek or Eastern Church (see Eastern Church under east)

orˈthodoxly adverb

orˈthodoxy noun

The state or quality of being orthodox

orthodromˈic adjective (Gr dromos a course or run; geography and nautical)

1. Having great circles represented as straight lines
2. (of nerve fibres) conducting or able to conduct impulses in the normal direction

orthodˈromy or orthodromˈics noun

Great-circle sailing, ie sailing by the most direct route

orthoepic /-epˈik/ or orthoepˈical adjective (Gr epos a word)

orthōˈepist (or /örˈthō-ep-ist/) noun

orthōˈepy (or /örˈthō-ep-i/) noun

(the study of) correct pronunciation

orthogenˈesis noun

1. (see genesis) the evolution of organisms systematically in definite directions and not accidentally in many directions
2. Determinate variation

orthogenˈesist noun

orthogenetˈic adjective

Relating to orthogenesis

orthogenetˈically adverb

orthogenˈic adjective

1. Orthogenetic
2. Concerning the treatment of mentally and emotionally disturbed children

orthogenˈics singular noun

orthognathˈic or orthogˈnathous adjective

(Gr gnathos jaw) having a lower jaw that neither protrudes nor recedes

orthogˈnathism noun

orthogˈonal adjective

(Gr gōniā angle) right-angled (orthogonal projection projection by lines perpendicular to the plane of projection)

orthogonalˈity noun

orthogˈonally adverb

orˈthograph noun

A drawing in orthographic projection, esp of the elevation of a building

orthogˈrapher noun

1. A person skilled in orthography
2. A speller

orthographˈic or orthographˈical adjective

1. Relating or according to spelling
2. Spelt correctly
3. In perspective projection, having the point of sight at infinity

orthographˈically adverb

orthogˈraphist noun

An orthographer

orthogˈraphy noun

1. (Gr orthographiā spelling or elevation; see -graphy) the art or practice of spelling words correctly
2. Spelling
3. Orthographic projection
4. Apparently for orthographer (Shakespeare)

orthokeratolˈogy noun

A technique for improving the vision of people affected by myopia and astigmatism, in which the cornea is temporarily reshaped by a special contact lens which is then removed and re-used as necessary

ortholˈogous adjective

orˈthologue noun

A gene that shares a common ancestry with, and has a similar DNA configuration to, a gene in a different species (cf paralogue)

orthomorphˈic adjective

(of a map) conformal

orthopaeˈdic or (N American) orthopēˈdic, also (rare) orthopaeˈdical or orthopēˈdical adjective

orthopaeˈdically or (N American) orthopēˈdically adverb

orthopaedics or (N American) orthopēdics /-pēˈdiks/, also orˈthopaedy or orˈthopēdy, formerly orthopedīˈa (or /-pēdˈ/) singular noun

(Gr pais, paidos a child) the art or process of curing deformities arising from (orig childhood) disease or injury of bones

orthopaeˈdist or orthopēˈdist noun

orthophosˈphate noun

An ordinary phosphate

orthophosphorˈic adjective

Phosphoric

orˈthophyre /-fīr/ noun

(orthoclase porphyry) a fine-grained syenitic rock with orthoclase crystals

orthophyric /-firˈik/ adjective

orthopinˈakoid noun

In monoclinic crystals, a form consisting of two faces parallel to the orthodiagonal and the vertical axis

orthopnoea /-thōp-nēˈə/ noun

(Gr orthopnoia, from pneein to breathe) a condition in which one can only breathe when upright

orˈthopod noun (med sl)

An orthopaedic surgeon

orˈthopraxis or orˈthopraxy noun

Correct or orthodox practice esp in religion (see praxis)

orˈthoprism noun

In monoclinic crystals, a form parallel to the orthodiagonal

orthopsychiatˈric adjective

orˈthopsychiatrist noun

orˈthopsychiatry noun

The branch of psychiatry concerned with the prevention and correction of incipient mental illness

Orthopˈtera plural noun

(see -ptera under ptero-) the cockroach order of insects with firm forewings serving as covers to the fanwise folded hind-wings

orthopˈteran noun and adjective

orthopˈterist or orthopterolˈogist noun

A person who studies the Orthoptera

orthopterolˈogy noun

orthopˈteroid adjective

orthopˈteron noun (pl orthopˈtera)

Any member of the Orthoptera

orthopˈterous adjective

Relating to the Orthoptera

orthopˈtic adjective

(Gr optikos optic) relating to normal vision

orthopˈtics singular noun

The treatment of defective eyesight by exercises and visual training

orthopˈtist noun

orthorexˈia noun (medicine)

A condition characterized by a morbid obsession with eating only foods considered healthy

orthorhomˈbic adjective (Gr rhombos rhomb; crystallography)

Referable to three unequal axes at right angles to each other

orthoscopˈic adjective

(Gr skopeein to look at) having or giving correct vision, true proportion, or a flat field of view

orthosilˈicate noun

A salt of orthosilicic /-sil-isˈik/ acid H₄SiO₄

orthōˈsis noun (pl orthōˈses)

A device that supports, corrects deformities in, or improves the movement of, the movable parts of the body

orthostatˈic adjective

1. (Gr orthostatos, from statos standing) standing erect
2. Connected with the erect posture

orthosˈtichous adjective

(Gr stichos a row) arranged in vertical rows

orthosˈtichy noun

A straight row, eg of leaves vertically over one another on an axis

orthotˈic adjective

Of or relating to orthotics

orthotˈics singular noun

The branch of medical science dealing with the rehabilitation of injured or weakened joints or muscles through artificial or mechanical support by orthoses

orˈthotist noun

Someone skilled in orthotics

orthotonēˈsis noun (Gr tonos accent; linguistics)

Accentuation of a proclitic or enclitic, opp to enclisis

orthotonˈic adjective

Taking an accent in certain positions but not in others, also orˈthotone

orthotopˈic adjective (Gr topos place; medicine)

(of tissue, grafts, organ replacement, etc) done, put, occurring, etc at the normal place

orthotropˈic adjective

1. (Gr tropos a turn) manifesting orthotropism
2. (of a material, such as wood) having elastic properties varying in different planes

• unpacking
• utu
• U-tube
• U-tubes
• U-turn
• U-turns
• utus
• UU
• uv
• UV
• uva
• UV-A
• UVA
• uvae
• uvarovite
• uvarovites
• uvas
• uva-ursi
• UV-B
• UVB
• UVC
• uvea
• uveal
• uveas
• uveitic