English Words Starting With O

• orthographize

  verb-intransitiveverb-transitiveVery Low
  /ɔːˈθɒɡrəfaɪz/To write or spell correctly according to standard spelling rules.
• orthography

  nounC1
  /ɔːˈθɒɡrəfi/A system of correct spelling and writing.
• orthohydrogen

  nounvery_low
  /ˌɔːθə(ʊ)ˈhaɪdrədʒən/A form of hydrogen gas where the spins of the two atomic nuclei are parallel.
• orthokeratology

  nounVery Low
  /ˌɔː.θəʊ.ˌkɛr.əˈtɒl.ə.dʒi/A non-surgical method using specially designed rigid contact lenses worn overnight to temporarily reshape the cornea and correct refractive errors like myopia.
• orthomorphic projection

  nounC2
  /ˌɔːθəˈmɔːfɪk prəˈdʒɛkʃən/A map projection that preserves correct shapes of small areas, i.e., it is conformal.
• orthopaedics

  nounC1
  /ˌɔːθəˈpiːdɪks/The branch of medicine concerned with the correction or prevention of deformities, disorders, or injuries of the skeleton and associated structures (muscles, ligaments, tendons).
• orthopedics

  nounC1
  /ˌɔː.θəˈpiː.dɪks/The branch of medicine concerned with the correction or prevention of deformities, disorders, or injuries of the skeleton and associated structures (muscles, ligaments).
• orthophosphate

  nounC2
  /ˌɔːθə(ʊ)ˈfɒsfeɪt/A salt or ester of phosphoric acid, containing the PO₄³⁻ ion.
• orthophosphoric acid

  nounC2
  /ˌɔːθəʊfɒsˈfɒrɪk ˈæsɪd/A specific, pure form of phosphoric acid (H₃PO₄) with a defined molecular structure, as opposed to other phosphoric acids like metaphosphoric or pyrophosphoric acid.
• orthophosphorous acid

  nounVery Low
  /ˌɔː.θəʊˈfɒs.fər.əs ˈæs.ɪd/A phosphorus oxoacid where phosphorus is in the +3 oxidation state, with the chemical formula H₃PO₃.
• orthophthalic acid

  nounVery Low
  /ˌɔː.θə(ʊ)ˈfθæl.ɪk ˈæs.ɪd/A specific type of phthalic acid where the carboxyl groups are adjacent (at positions 1 and 2) on the benzene ring. It's a key chemical precursor for unsaturated polyester resins.
• orthopnea

  nounC2/Professional
  /ˌɔː.θɒpˈniː.ə/A condition of difficult or labored breathing which occurs when lying flat, relieved by sitting up or standing.
• orthopod

  nounLow
  /ˈɔːθəpɒd/A doctor who specializes in the branch of medicine dealing with the correction of deformities of bones or muscles.
• orthopraxia

  nounC2
  /ˌɔːθə(ʊ)ˈpræksɪə/The correct practice or conduct, especially in a religious context; emphasis on action and behavior over belief.
• orthopraxy

  nounC2 / Very Low Frequency
  /ˈɔː.θəˌprak.si/Correctness or orthodoxy of action or conduct; the practical aspect of a belief system, emphasizing correct practice over correct belief.
• orthopsychiatry

  nounC2
  /ˌɔːθəʊsaɪˈkaɪətri/A branch of psychiatry concerned with the prevention and treatment of behavioral and emotional disorders, especially in children and adolescents.
• orthopter

  nounVery low
  /ɔːˈθɒptə/An aircraft that gains lift from wings that move up and down, like an insect's wings.
• orthopteran

  adjectivenounLow
  /ɔːˈθɒpt(ə)rən/any insect of the order Orthoptera, characterized by straight, narrow forewings and large, membranous hindwings for jumping, including grasshoppers, crickets, and katydids.
• orthopteron

  nounVery Low
  /ɔːˈθɒptərən/An insect of the order Orthoptera, characterized by straight, narrow wings, chewing mouthparts, and typically large hind legs for jumping.
• orthoptics

  nounC1
  /ɔːˈθɒptɪks/A healthcare specialty focused on diagnosing and managing disorders of binocular vision, eye movements, and alignment (e.g., strabismus, amblyopia).

Showing 2081–2100 of 3187 words.