English Words Starting With O

• optical tweezers

  nounVery Low
  /ˈɒp.tɪ.kəl ˈtwiː.zəz/A scientific instrument that uses highly focused laser beams to trap and manipulate microscopic particles, such as atoms, viruses, and biological cells, without physical contact.
• optical wedge

  nounC2
  /ˈɒptɪkəl wɛdʒ/A piece of glass or other transparent material with flat, non-parallel faces, used in optical systems to gradually change the angle of light or to measure small angles.
• optician

  nounB2
  /ɒpˈtɪʃ.ən/A person who is qualified to make and sell eyeglasses and contact lenses to correct vision problems, based on a prescription from an optometrist or ophthalmologist.
• opticist

  nounC1/C2 (Very low frequency, technical term)
  /ˈɒp.tɪ.sɪst/A person who designs or makes lenses, optical instruments, or works professionally in the field of optics.
• optics

  nounC1
  /ˈɒp.tɪks/The branch of physics that studies light and vision.
• optime

  nounVery Low
  /ˈɒptɪmiː/A graduate achieving second-class honours in mathematics from the University of Cambridge, UK.
• optimism

  nounB2
  /ˈɒptɪmɪzəm/A tendency to expect the best possible outcome in any situation; a hopeful and positive outlook on life and the future.
• optimist

  nounB2
  /ˈɒptɪmɪst/A person who expects favorable outcomes and focuses on the positive aspects of situations.
• optimize

  verbverb-intransitiveverb-transitiveB2
  /ˈɒptɪmaɪz/To make something as effective, efficient, or perfect as possible.
• optimum

  adjectivenounB2
  /ˈɒptɪməm/The best or most favorable condition, degree, or amount for a particular purpose; most conducive to a favorable outcome.
• optimum population

  nounLow
  /ˈɒp.tɪ.məm ˌpɒp.jəˈleɪ.ʃən/The number of people in a given area that allows for the highest quality of life or the most efficient use of resources, balancing needs with environmental sustainability.
• option

  nounverbverb-transitiveHigh-frequency (B1+). Extremely common in all registers.
  /ˈɒp.ʃən/One of a number of things from which only one can be chosen; a choice or alternative.
• option money

  nounMedium
  /ˈɒp.ʃən ˌmʌn.i/A non-refundable payment (option fee) made by a prospective buyer to a seller to secure the exclusive right to purchase a property within a specified period. If the buyer proceeds, the fee is typically credited toward the purchase price.
• optionee

  nounLow
  /ˌɒpʃəˈniː/A person who holds or has been granted an option, typically to purchase something like property or stock.
• optoelectronics

  nounC1
  /ˌɒptəʊɪlɛkˈtrɒnɪks/The branch of electronics that deals with devices and systems that source, detect, and control light.
• optometer

  nounVery Low
  /ɒpˈtɒmɪtə/An instrument for measuring the refractive power of the eye.
• optometrist

  nounLow-frequency, domain-specific
  /ɒpˈtɒm.ə.trɪst/A healthcare professional who examines eyes for vision defects, prescribes corrective lenses, and diagnoses certain eye conditions. They are not medical doctors who perform surgery.
• optometry

  nounC1
  /ɒpˈtɒm.ə.tri/The practice or profession of examining the eyes for vision defects and prescribing corrective lenses.
• optophone

  nounVery Low / Obsolete
  /ˈɒptəfəʊn/A device that converts light into sound, historically used to enable blind people to read printed text.
• optotype

  nounC1/C2 (Specialist/Technical)
  /ˈɒp.tə.taɪp/A standardised letter, number, or symbol used on an eye chart to measure visual acuity.

Showing 1601–1620 of 3187 words.