English Words Starting With R

• radium emanation

  nounC2/Extremely Low
  /ˈreɪdiəm ˌɛməˈneɪʃ(ə)n/A former name for the gaseous radioactive element radon, specifically the isotope radon-222 (Rn-222), produced from the radioactive decay of radium.
• radium f

  nounC1/C2
  /ˈreɪdiəm/A highly radioactive metallic chemical element (symbol Ra) discovered by Marie and Pierre Curie, which glows faintly in the dark due to its radioactivity and was formerly used in luminous paints and cancer treatments.
• radium sulfate

  nounLow/Very Specialised
  /ˈreɪdiəm ˈsʌlfeɪt/A white, insoluble, radioactive crystalline salt of radium, RaSO₄, used historically in radiotherapy.
• radium therapy

  nounLow
  /ˈreɪdiəm ˈθɛrəpi/The medical use of radium as a source of radiation to treat diseases, particularly cancer.
• radius

  nounB2
  /ˈreɪ.di.əs/A straight line from the center to the circumference of a circle or sphere; a measure of distance from a central point.
• radius of action

  nounLow
  /ˈreɪdiəs əv ˈækʃ(ə)n/The maximum distance from a base or source that a person, vehicle, or force can operate effectively, usually implying a round trip.
• radius of convergence

  nounLow
  /ˈreɪ.di.əs əv kənˈvɜː.dʒəns/In mathematics, a non-negative real number that represents the distance from the centre of a power series within which the series converges.
• radius of curvature

  nounC2
  /ˈreɪdiəs əv ˈkɜː.və.tʃər/A scalar measure of how sharply a curve bends at a particular point, defined as the radius of the osculating circle (the circle that best approximates the curve at that point).
• radius of gyration

  nounLow (C2)
  /ˌreɪ.di.əs əv dʒaɪˈreɪ.ʃən/A mathematical quantity describing the distribution of an object's mass around its axis of rotation, specifically the root-mean-square distance of its particles from that axis.
• radius rod

  nounC2
  /ˈreɪ.di.əs ˌrɒd/A rigid bar or rod in a vehicle's suspension system that helps control the position of the axle, preventing forward/backward movement.
• radius vector

  nounC2
  /ˈreɪdɪəs ˈvɛktə/In mathematics and physics, a line segment drawn from a fixed origin point to a moving point, typically used to describe position in polar coordinates or orbits.
• radix

  nounC2 (Very Low Frequency / Specialized)
  /ˈreɪ.dɪks/A root, base, or source from which something develops.
• radix point

  nounSpecialized
  /ˈreɪdɪks pɔɪnt/The symbol used in positional numeral systems to separate the integer part from the fractional part of a number, such as the decimal point in base-10 or binary point in base-2.
• radnor

  nounLow
  /ˈrædnə/A proper noun referring primarily to a historic county in Wales, a town within it, and a geographic area.
• radnorshire

  nounVery Low
  /ˈrædnəˌʃə/A historic county in east-central Wales, UK, that existed until 1974.
• radom

  nounLow
  A common misspelling of 'random', meaning lacking a definite plan, purpose, or pattern.
• radome

  nounLow (Specialized)
  /ˈreɪ.dəʊm/A protective covering or dome housing a radar antenna.
• radon

  nounC1
  /ˈreɪdɒn/A chemical element (Rn, atomic number 86), a radioactive, colourless, odourless, inert noble gas.
• radula

  nounC2
  /ˈradjʊlə/The flexible, ribbon-like tongue of molluscs, especially gastropods, covered in microscopic, backward-pointing teeth used for scraping or cutting food.
• radwaste

  nounLow-frequency, technical term.
  /ˈræd.weɪst/Radioactive waste; hazardous material left over from processes involving nuclear reactions, such as nuclear power generation or weapons production.

Showing 341–360 of 5802 words.