English Words Starting With O

• operations research

  nounC1
  /ˌɒp.ərˈeɪ.ʃənz rɪˈsɜːtʃ/A discipline that uses advanced analytical methods (like mathematical modeling, statistics, and algorithms) to make better decisions and optimize complex systems in business, industry, or government.
• operations room

  nounLow-Frequency (C1/C2)
  /ˌɒp.əˈreɪ.ʃənz ˌruːm/A dedicated, often secure room where a complex activity (military, emergency, industrial) is centrally monitored, coordinated, and controlled.
• operative

  adjectivenounC1
  /ˈɒp.ər.ə.tɪv/Functioning effectively; in operation; having effect.
• operatize

  verbVery rare
  /ˈɒpərətaɪz/To turn something (such as a business or idea) into an operational system; to systematize or implement as a functioning process.
• operator

  nounB2
  /ˈɒpəreɪtə(r)/A person who operates or controls a machine, equipment, or system; a person or company that runs a business or service.
• operatory

  adjectivenounLow
  /ˈɒp(ə)rət(ə)ri/A room or set of rooms equipped for performing surgical or dental operations.
• opercle

  nounC2
  /ˈɒpək(ə)l/A thin, bony plate or lid covering an opening, especially in fish anatomy.
• operculum

  nounC2
  /əʊˈpɜːkjʊləm/A cover or lid, especially a flap or bony structure covering an opening in an organism.
• operetta

  nounC2
  /ˌɒp.ərˈet.ə/A short, light-hearted opera, often with spoken dialogue.
• operon

  nounC2
  /ˈɒpərɒn/A functional unit of DNA in bacteria containing a cluster of genes under the control of a single promoter.
• ophelia

  nounLow
  /əˈfiːliə/A female given name, most famously the character from Shakespeare's Hamlet.
• opheltes

  nounExtremely Rare
  /ˈɒfəlˌtiːz/A mythological name; specifically the infant hero Opheltes, whose death led to the founding of the Nemean Games.
• ophicleide

  nounVery Rare / C2+
  /ˈɒfɪklaɪd/A large, now obsolete brass keyed bass bugle instrument used in 19th-century orchestras and military bands.
• ophidian

  adjectivenounC2
  /ə(ʊ)ˈfɪdɪən/of or relating to snakes; snakelike.
• ophidiid

  adjectivenounRare/Very Low
  /əʊˈfɪdɪɪd/A fish belonging to the Ophidiidae family, which includes cusk-eels and other elongated, bottom-dwelling marine species.
• ophiolatry

  nounExtremely Rare
  /ˌɒfɪˈɒlətri/The worship of snakes or serpents.
• ophiolite

  nounC2
  /ˈɒfɪəlʌɪt/A distinctive assemblage of mafic and ultramafic rocks found in orogenic belts, interpreted as fragments of ancient oceanic crust and upper mantle thrust onto continental margins.
• ophiology

  nounVery low frequency (specialist/technical term)
  /ˌɒfiˈɒlədʒi/The branch of zoology concerned with the study of snakes.
• ophir

  nounC2/Extremely Rare
  /ˈəʊfə/A biblical region mentioned in the Old Testament, famous for its gold.
• ophite

  nounObscure
  /ˈəʊfʌɪt/A rock composed of green minerals, specifically a green diabase.

Showing 1461–1480 of 3187 words.