What is "r"

R \R\ ([aum]r). R, the eighteenth letter of the 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. [1913 Webster] The English letter derives its form from the Greek through the Latin, the Greek letter being 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.

In a circle, meaning "registered (trademark)," first incorporated in U.S. statues 1946. R&R "rest and relaxation," first recorded 1953, American English; R&B "rhythm and blues" (type of popular music) first attested 1949, American English.\n\nIf all our r's that are written are pronounced, the sound is more common than any other in English utterance (over seven per cent.); the instances of occurrence before a vowel, and so of universal pronunciation, are only half as frequent. There are localities where the normal vibration of the tip of the tongue is replaced by one of the uvula, making a guttural trill, which is still more entitled to the name of "dog's letter" than is the ordinary r; such are considerable parts of France and Germany; the sound appears to occur only sporadically in English pronunciation. [Century Dictionary]\n

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\nThe moment we encounter the added r's of purp or dorg in our reading we know that we have to do with humor, and so with school-marm. The added consonants are supposed to be spoken, if the words are uttered, but, as a matter of fact, they are less often uttered than seen. The words are, indeed, largely visual forms; the humor is chiefly for the eye.

[Louise Pound, "The Humorous 'R,'" "American Mercury," October 1924]

\nShe goes on to note that in British humorous writing, -ar "popularly indicates the sound of the vowel in father" and formations like larf (for laugh) "are to be read with the broad vowel but no uttered r." She also quotes Henry James on the characteristic prominence of the medial -r- sound (which tends to be dropped in England and New England) in the speech of the U.S. Midwest, "under some strange impulse received toward consonantal recovery of balance, making it present even in words from which it is absent, bringing it in everywhere as with the small vulgar effect of a sort of morose grinding of the back teeth."

Etymology 1 letter (Latn-def en letter 18 ar) num. (Latn-def en ordinal 18 ar) Etymology 2

vb. (context abbreviation slang text messaging internet English) are (qualifier: in text messaging and internet conversations)

The grapheme Ȓ ( lower case ȓ) is a letter used in discussion of Croatian phonetics.

R is a programming language and software environment for statistical computing and graphics supported by the R Foundation for Statistical Computing. The R language is widely used among statisticians and data miners for developing statistical software and data analysis. Polls, surveys of data miners, and studies of scholarly literature databases show that R's popularity has increased substantially in recent years.

R is a GNU package. The source code for the R software environment is written primarily in C, Fortran, and R. R is freely available under the GNU General Public License, and pre-compiled binary versions are provided for various operating systems. While R has a command line interface, there are several graphical front-ends available.

The grapheme Ř, ř ( R with háček, example of Czech pronunciation: ) is a letter used in alphabets of the Czech, Upper Sorbian, and Silesian languages. A similar consonant can also be found in some Norwegian dialects around Narvik and in Berber (especially in its Rif variety). However, of the official national languages, only Czech has it.

The Unicode glyphs are and . Either can also be represented using the combining character .

Ŕ ( minuscule: ŕ) is a letter of the Slovak and Lower Sorbian alphabets. It is formed from R with the addition of an acute. Their Unicode codepoints are and . The PS names are Racute and racute.

In computational complexity theory, R is the class of decision problems solvable by a Turing machine, which is the set of all recursive languages.

R is the eighteenth letter of the Latin alphabet.

R may also refer to:

R Cable y Telecomunicaciones Galicia, S.A. is a Spanish telecommunications company that offers fixed and mobile telephone, television and Broadband Internet services to businesses and consumers in Galicia, Spain.

R was a line operated by the Los Angeles Railway from 1895 to 1958, and by the Los Angeles Metropolitan Transit Authority from 1958 to 1963.

R is a 2010 Danish prison drama film written and directed by Tobias Lindholm and Michael Noer, and starring Pilou Asbæk. The film was produced by Nordisk Film. The film follows Rune Pedersen (Pilou Asbæk), who is serving a prison sentence of two years in Horsens State Prison. Here he is set to do the dirty work of distributing drugs between departments.

The R Broadway Local is a rapid transit service in the B Division of the New York City Subway. Its route emblem, or "bullet", is colored since it uses the BMT Broadway Line in Manhattan. The R operates local between 71st Avenue in Forest Hills, Queens and 95th Street in Bay Ridge, Brooklyn at all times except nights when it short turns at 36th Street in Sunset Park with northbound trains bypassing 53rd and 45th Streets. Although the R does not have any outdoor stations along its entire run, there is a small portion on the BMT Fourth Avenue Line between 59th Street and Bay Ridge Avenue that passes over a cut containing the Long Island Rail Road's Bay Ridge Branch tracks.

R is the ratio of the hadronic cross section to the muon cross section in electron– positron collisions:

$$R = \frac{\sigma^{(0)}(e^+e^-\rightarrow \mathrm{hadrons})}{\sigma^{(0)}(e^+e^-\rightarrow \mu^+\mu^-)},$$

where the superscript (0) indicates that the cross section has been corrected for initial state radiation. R is an important input in the calculation of the anomalous magnetic dipole moment. Experimental values have been measured for center-of-mass energies from 400 MeV to 150 GeV.

R also provides experimental confirmation of the electric charge of quarks, in particular the charm quark and bottom quark, and the existence of three quark colors. A simplified calculation of R yields

R = 3∑e, 

where the sum is over all quark flavors with mass less than the beam energy. e is the electric charge of the quark, and the factor of 3 accounts for the three colors of the quarks. QCD corrections to this formula have been calculated.