from The American Heritage® Dictionary of the English Language, 4th Edition

  • A trademark used for a movie rating indicating that admission will be granted only to persons of or over a certain age, usually 17, unless accompanied by a parent or guardian.
  • The symbol for gas constant.
  • The symbol for radical.
  • abbr. range (surveying)
  • abbr. Réaumur (scale)
  • abbr. registered trademark
  • abbr. Republican
  • abbr. Ecclesiastical response
  • abbr. right
  • abbr. roentgen
  • abbr. rook (chess)
  • abbr. Baseball run

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. The eighteenth letter of the basic modern Latin alphabet.
  • n. roentgen (unit)
  • n. resistance (in electricity)
  • n. IUPAC 1-letter abbreviation for any purine
  • n. IUPAC 1-letter abbreviation for arginine
  • n. The eighteenth letter of the English alphabet, called ar and written in the Latin script.
  • n. The ordinal number eighteenth, derived from this letter of the English alphabet, called ar and written in the Latin script.
  • abbr. Republican
  • abbr. restricted
  • abbr. reverse
  • abbr. right (as opposed to left)
  • abbr. ring
  • abbr. rook
  • abbr. The statistic reporting the number of runs scored by a player
  • abbr. Thursday


This definition is lacking an etymology or has an incomplete etymology. You can help Wiktionary by giving it a proper etymology. (Wiktionary)


  • It is interesting that the Drake equation has SFR as the first item R* R star, which was originally given by Drake as "the average rate of star formation in the galaxy"

    If the Earth is Rare, We May Not Hear from ET | Universe Today

  • (Anderson was an R-- a very progressive R, and Rolvaag was DFL).

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  • Joynr post 7/31/7 PA 2298 R 297 R% 12.92 H 538 BA 265 bb/pa 9.09 Slg 449.

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  • Recall that a relation R stands to its ancestral R* as the relation is a parent of stands to is an ancestor of.

    Plural Quantification

  • S among the members of P, everyone conforms to R; everyone expects everyone else to conform to R; everyone has approximately the same preferences regarding all possible combinations of actions; everyone prefers that everyone conform to R, on condition that at least all but one conform to R; everyone would prefer that everyone conform to R², on condition that at least all but one conform to

    Common Knowledge

  • And since we all know who is doing it, we should stop arguing No on Prop R-----it is No on Prop R slamdunk--and get the mayor's office to tell us who this sub one percenter is so he can be out of our goverment for good.

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  • You said Hume and any similarly situated agnostic has a defeater for R, a belief to which he is inclined by nature -- and you added that the rational course for them therefore is to give up belief in R-- provided they have no other information about the reliability of their faculties.

    Warranted Christian Belief

  • We ought to understand that the total interval (0, 1) say, has a probability, but certain point sets in (0, 1), like R or R′, are of type

    Dictionary of the History of Ideas

  • The conclusion (Tornier, Geiringer) is that to the set R (and to R′) no probability can be assigned in a frequency theory.

    Dictionary of the History of Ideas

  • The single “trial” consists of as many draws as needed to decide whether this decimal is rational or not (belongs to R or to R′).

    Dictionary of the History of Ideas


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