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Meaning of R

Pronunciation:  âr, âr

WordNet Dictionary
  1. [n]  the length of a line segment between the center and circumference of a circle or sphere
  2. [n]  the 18th letter of the Roman alphabet
  3. [n]  (physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole
  4. [n]  a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air

R is a 1 letter word that starts with R.


 Synonyms: gas constant, radius, roentgen, universal gas constant
 See Also: alphabetic character, constant, diam, diameter, length, letter, letter of the alphabet, radioactivity unit, radius of curvature, Roman alphabet, semidiameter



Webster's 1913 Dictionary
  1. \R\ ([aum]r).
    R, the eighteenth letter of English alphabet, is a vocal
    consonant. It is sometimes called a semivowel, and a liquid.
    See Guide to Pronunciation, [sect][sect] 178, 179, and
    250-254. ``R is the dog's letter and hurreth in the sound.''
    --B. Jonson.
    Note: In words derived from the Greek language the letter h
          is generally written after r to represent the aspirated
          sound of the Greek "r, but does not affect the
          pronunciation of the English word, as rhapsody,
          rhetoric. The English letter derives its form from the
          Greek through the Latin, the Greek letter derived from
          the Ph[oe]nician, which, it is believed, is ultimately
          of Egyptian origin. Etymologically, R is most closely
          related to l, s, and n; as in bandore, mandole; purple,
          L. purpura; E. chapter, F. chapitre, L. capitulum; E.
          was, were; hare, G. hase; E. order, F. ordre, L. ordo,
          ordinis; E. coffer, coffin.
    {The three Rs}, a jocose expression for reading, (w)riting,
       and (a)rithmetic, -- the fundamentals of an education.