English Words Starting With R

• radial tire

  nounC1
  /ˈreɪ.di.əl ˈtaɪə/A modern vehicle tire constructed with cords (plies) that run perpendicularly from the bead across the tread, under the belt, providing improved strength, fuel efficiency, and handling compared to older bias-ply designs.
• radial triangulation

  nounC2
  /ˌreɪ.di.əl traɪˌæŋ.ɡjʊˈleɪ.ʃən/A surveying or mapping method where measurements are taken from a single central point to surrounding points to determine positions.
• radial tyre

  nounC1
  /ˈreɪ.di.əl ˈtaɪə/A tyre in which the fabric layers (plies) run straight across from bead to bead, with additional belts under the tread, providing better road contact and durability.
• radial velocity

  nounlow
  /ˌreɪ.di.əl vəˈlɒs.ə.ti/The component of an object's velocity that is directed along the line of sight from the observer, specifically either directly toward or away from the observer.
• radian

  nounC2
  /ˈreɪ.di.ən/A unit of angle measure in the International System of Units (SI), defined as the angle subtended at the centre of a circle by an arc equal in length to the radius of the circle.
• radiance

  nounB2
  /ˈreɪ.di.əns/A bright, glowing light shining from something; also, a quality of happiness, health, or beauty that seems to shine from a person.
• radiancy

  nounLow (literary/formal)
  /ˈreɪ.di.ən.si/The quality or state of emitting or reflecting light brightly; radiant brightness.
• radiant

  adjectivenounB2
  /ˈreɪ.di.ənt/sending out light; shining or glowing brightly; showing great happiness, health, or beauty
• radiant efficiency

  nounC2 / Very Low Frequency
  /ˈreɪ.di.ənt ɪˈfɪʃ.ən.si/A technical measure of how effectively a source converts input energy into visible electromagnetic radiation (light), typically expressed as a percentage or ratio.
• radiant emittance

  nounVery low
  /ˈreɪ.di.ənt ɪˈmɪt.əns/The total radiant flux (electromagnetic power) emitted by a surface per unit area.
• radiant energy

  nounLow in general use; medium-high in technical/scientific contexts.
  /ˈreɪdɪənt ˈɛnədʒi/Energy that travels in the form of waves or particles, particularly through empty space or a medium, as electromagnetic radiation (e.g., light, heat).
• radiant exitance

  nounVery low
  /ˈreɪ.di.ənt ɪkˈsaɪ.təns/The total radiant flux emitted by a surface per unit area, measured in watts per square metre.
• radiant flux

  nounC1
  /ˈreɪ.di.ənt flʌks/The total power of electromagnetic radiation (including visible light) emitted, transmitted, or received by a surface or object, measured in watts.
• radiant heat

  nounC1
  /ˈreɪ.di.ənt hiːt/Heat transferred by electromagnetic waves (infrared radiation) without heating the intervening medium, directly warming objects and surfaces it strikes.
• radiant heating

  nounC1
  /ˈreɪ.di.ənt ˈhiː.tɪŋ/A system for warming a room or building through heat radiating from warmed panels or pipes in the floor, walls, or ceiling, rather than by heating air directly.
• radiant intensity

  nounC1
  /ˈreɪdiənt ɪnˈtɛnsəti/The power of electromagnetic radiation per unit solid angle emitted from a point source in a particular direction.
• radiata

  nounVery Low
  /ˌreɪ.diˈeɪ.tə/The class of radially symmetrical animals, chiefly comprising jellyfish, corals, and sea anemones (Cnidaria) and comb jellies (Ctenophora).
• radiata pine

  nounC2
  /ˌreɪ.diˈeɪ.tə paɪn/A fast-growing pine tree (Pinus radiata) native to California and widely planted for timber, especially in the Southern Hemisphere.
• radiate

  adjectiveverbverb-intransitiveverb-transitiveB2
  /ˈreɪ.di.eɪt/to send out rays, light, heat, or energy from a central point; to spread outward from a center.
• radiation

  nounC1
  /ˌreɪ.diˈeɪ.ʃən/Energy in the form of waves or particles, especially heat or light, sent out from a source.

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