English Words Starting With O

• orthoclase

  nounVery low
  /ˈɔːθə(ʊ)kleɪz/A common rock-forming mineral of the feldspar group.
• orthodontia

  nounC1
  /ˌɔːθəˈdɒn.ti.ə/The branch of dentistry that deals with the diagnosis, prevention, and correction of misaligned teeth and jaws.
• orthodontics

  nounC1
  /ˌɔːθəˈdɒntɪks/The branch of dentistry that specializes in diagnosing, preventing, and correcting misaligned teeth and jaws.
• orthodonture

  nounLow frequency (much less common than 'orthodontics')
  /ˌɔːθəˈdɒntʃə/The professional field concerned with the diagnosis, prevention, and correction of malpositioned teeth and jaws.
• orthodox church

  nounB2
  /ˈɔːθədɒks tʃɜːtʃ/A collective term for the Eastern Christian churches that derive from the Byzantine tradition, recognize the seven ecumenical councils, and are in communion with the Ecumenical Patriarch of Constantinople.
• orthodox jew

  nounB2
  /ˈɔːθədɒks dʒuː/A Jewish person who adheres to a traditional, theologically conservative interpretation of Jewish law (Halakha) and tradition.
• orthodox judaism

  nounC2
  /ˌɔː.θə.dɒks ˈdʒuː.deɪ.ɪ.zəm/A major branch of Judaism that adheres strictly to traditional Jewish law (Halakha), beliefs, and practices, as derived from the Torah and Rabbinic tradition.
• orthodox sleep

  nounVery Low
  /ˈɔːθədɒks sliːp/A technical term for the stage of sleep characterized by slow brain waves, relaxed muscles, and no rapid eye movement.
• orthodoxy

  nounC1
  /ˈɔːθədɒksi/The authorized or generally accepted theory, doctrine, or practice, especially in religion.
• orthoepy

  nounC2 / Very Low
  /ˈɔː.θəʊ.ˌiː.pi/ or /ˈɔː.θəʊ.ˌep.i/The study or rules of correct pronunciation of a language, especially its standard pronunciation.
• orthoformate

  nounVery Low / Technical
  /ˌɔːθə(ʊ)ˈfɔːmeɪt/A chemical compound of the general structure HC(OR)3, derived from formic acid by replacing the carbonyl oxygen and hydrogen with alkoxy groups (OR).
• orthoformic acid

  nounVery Low (Specialist)
  /ˌɔːθə(ʊ)ˈfɔːmɪk ˈæsɪd/a specific chemical compound, formally recognized as methanetriyl triformate, with the formula HC(OC(O)H)₃, used as a reagent in organic synthesis.
• orthogenesis

  nounC2
  /ˌɔːθəʊˈdʒɛnɪsɪs/The biological theory that evolution follows a predetermined, straight-line path towards increasing complexity or a specific goal.
• orthognathic surgery

  nounC2 (Very Low Frequency)
  /ˌɔː.θəɡˈnæθ.ɪk ˈsɜː.dʒər.i/A surgical procedure to correct irregularities or misalignment of the jawbones.
• orthogonal matrix

  nounLow
  /ɔːˈθɒɡənl̩ ˈmeɪtrɪks/In linear algebra, a square matrix whose transpose is equal to its inverse, meaning its rows and columns are orthonormal vectors.
• orthogonal projection

  nounC2
  /ɔːˌθɒɡənl prəˈdʒɛkʃn/A geometric operation where a point, line, or shape is mapped onto a line or plane by dropping a perpendicular from the original object to the target line or plane.
• orthogonal trajectory

  nounC2
  /ɔːˈθɒɡənəl trəˈdʒɛktəri/A curve that intersects every member of a given family of curves at right angles (90 degrees).
• orthogonalize

  verb-transitiveC2
  /ɔːˈθɒɡənəlaɪz/To make orthogonal, i.e., to transform or arrange vectors or data points so that they are perpendicular or statistically independent.
• orthographer

  nounRare
  /ɔːˈθɒɡ.rə.fər/A person who is skilled in or writes about correct spelling.
• orthographic projection

  nounC2
  /ˌɔː.θəˈɡræf.ɪk prəˈdʒek.ʃən/A method of representing a three-dimensional object in two dimensions using parallel lines perpendicular to the projection plane, showing multiple views (e.g., front, top, side).

Showing 2061–2080 of 3187 words.