This article is on the letter "R", for other uses go to R (disambiguation).

The letter R is the eighteenth letter in the Latin alphabet. Its name in English is ar, pronounced (with mute -r) in Received Pronunciation and other non-rhotic accents of English, [ɑ:ɹ in General American and other rhotic accents.

History

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Egyptian hieroglyph tp	Proto-Semitic R	Phoenician R	Etruscan R	Greek Rho	Later Etruscan R	-	D1

The original Semitic letter was probably inspired by an Egyptian hieroglyph for "head", pronounced t-p in Egyptian, but it was used for R by Semites because in their language, the word for "head" was Rêš (also the name of the letter). It developed into Greek Ρ (Rhô) and Latin R. It is likely that some Etruscan forms of the letter added the extra stroke to distinguish it from a later form of the letter P, although the similarity of the proto-Semitic glyph to the modern form with the added stroke is striking.

Minuscule

The minuscule (lower-case) form of r developed through several variations on the capital form. In handwriting it was common not to close the bottom of the loop but continue into the leg, saving an extra pen stroke. The loop-leg stroke shortened into the simple arc used today.

Another minuscule, the r rotunda, kept the loop-leg stroke but dropped the vertical stroke. It fell out of use around the 18th century.

Pronunciation of R

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See rhotic consonant, r-colored vowel, and guttural R for discussion of the family of 'r' sounds.

In the International Phonetic Alphabet, 'r' represents the alveolar trill sound.

Alveolar trill /r/	alveolar trill.ogg	Arabic, Armenian, British English (in emphatic speech), Finnish, German in performance arts, Italian, Polish, Portuguese, Romanian, Scots, Spanish 'rr'
Alveolar approximant /ɹ/	alveolar approximant.ogg	English (most varieties)
Alveolar flap / Alveolar tap /ɾ/	alveolar flap.ogg	Greek, Hindi 'र', Portuguese, Spanish 'r'
Alveolar lateral flap /ɺ/	Con-80b.wav	Japanese
Retroflex approximant /ɻ/	Retroflex approximant.ogg	American English for some speakers
Retroflex flap /ɽ/	Retroflex flap.ogg	Hindi 'ड़', Norwegian, sometimes Scottish English
Uvular trill /ʀ/	Uvular trill.ogg	French; German; some dialects of Dutch, Italian and Swedish
Voiced uvular fricative /ʁ/	voiced uvular fricative.ogg	Danish, Dutch, French, German, Hebrew
Voiced velar fricative /ɣ/	voiced velar fricative.ogg	Armenian

Meanings for R

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• In architecture, R-value is a non-SI measure of thermal resistance used in housing insulation.
• In astronomy,
  • R stands for planetary ring, as in R/2003 U 1 (the first ring sighted around Uranus in 2003).
  • R stands for a September 1 through 15 discovery, in the provisional designation of a comet (e.g. C/1882 R1, the Great September Comet of 1882) or asteroid (e.g. (4211) 1987 RT).
• In biochemistry, R is the symbol for arginine
• In calendars, R is often used as an abbreviation for Thursday instead of T, to avoid confusion with Tuesday
• In chemistry,
  • R denotes the gas constant
  • In organic chemistry, R (from German Rest) is the symbol for an unspecified hydrocarbon chain
  • In stereochemistry, R (rectus) signifies clockwise arrangement of substituents around a carbon atom using the Cahn Ingold Prelog priority rules
• In chess, R is a notation symbol for the rook piece
• In the RGB colour model, R stands for the colour red
• In commerce, R with an enclosing circle, ®, denotes a registered trademark
• In complexity theory, R is a commonly-used name for two complexity classes:
  • The class of recursive languages
  • The class of languages solvable in probabilistic polynomial-time with one-sided error, also called RP
• In computing,
  • R is the name of a statistical programming language based on S; see R programming language
  • r is sometimes used as the symbol for the rune 16-bit unit
  • An R-value is the expression on the right-hand-side of an assignment or (in)equality operator.
• In driving a motor vehicle, R designates the reverse gear of a transmission
• In electrical engineering, R is often the symbol for electrical resistance
• In film, R is a rating given for films given by film classification boards (such as the Motion Picture Association of America in the US), meaning "restricted"; see R (rating)
  • R is a character in the James Bond films The World Is Not Enough as well as video game 007 Racing
• In finance, R is the U.S. ticker symbol for Ryder Systems Inc.
• In foreign exchange, R is the symbol for the currency of South Africa, the rand.
• In geometry, r is often a variable for the radius of a circle
• In geotechnical engineering, R-value is a property of soils used in pavement design.
• In law, the abbreviation R. or R stands for either Rex (King) or Regina (Queen) depending on the gender of the British monarch at the time. The title is mostly used by Commonwealth countries in citing a criminal case to represent the prosecuting party (i.e. The Crown). In the United States, the term "United States" is usually used, or informally "the people" is sometimes used.
  • For the same reason, the personal signature of a British monarch consists of the monarch's regnal name followed by the letter R. For example, Queen Elizabeth II signs official documents as "Elizabeth R". This is typical for most monarchies, such as Norway, where the king signs official documents as "Harald R".
• In mathematics,
  • the symbol ℛ (script capital R, Unicode $211B) represents the Riemann integral
  • the symbol ℜ (black-letter capital R, Unicode $211C) represents the real part of a complex number
  • blackboard bold $\backslash mathbb\{R\}$ or ℝ (double-struck capital R, Unicode $211D) represents the set of all real numbers
  • r is occasionally used as a variable to stand for a prime number that is somehow larger that two other prime numbers p and q. For example, an arbitrary sphenic number n can be expressed as $n\; =\; pqr$ where .
  • An R-value is the expression on the right-hand-side of an inequality statement.
• In music,
  • R, also known as Rated R (album) is a Queens of the Stone Age album.
  • R., is an a 1998 album by R. Kelly
  • The R is the nickname of the rapper Rakim.
• In navigation, R denotes the relative direction "right"; see left and right
• In physics,
  • R is a gas constant
  • R is the symbol for the roentgen, a unit of dosage of ionising radiation
  • °R or °Ra is the symbol for the Rankine degree
  • °R or °Ré is the symbol for the Réaumur degree
  • °R or °Rø is the symbol for the Rømer degree
  • R is the symbol of the rayleigh, a unit of luminous flux used to measure air glow
  • r stands for revolution in units of measure of angular velocity such as the revolution per second (rps)
• As the first letter of a postal code,
  • In Canada, R stands for Manitoba.
• In radiocommunication, R is one of the ITU prefixes allocated to Russia
• In the romanization of the Japanese language, the letter R was selected instead of the letter L for the syllables in the tenth tier of the kana, for both the Hepburn system and the Kunrei, amongst others.
• In statistics,
  • R is the name of a statistical programming language based on S; see R programming language
  • r is the Pearson product-moment correlation coefficient
• In chemical engineering, r denotes the molar formation rate per volume (mol s^-1 m^-3)
• the 3 Rs (Reading, wRiting and aRithmetic)

Codes for computing

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In Unicode the capital R is codepoint U+0052 and the lowercase r is U+0072.

The ASCII code for capital R is 82 and for lowercase r is 114; or in binary 01010010 and 01110010, correspondingly.

The EBCDIC code for capital R is 217 and for lowercase r is 153.

The numeric character references in HTML and XML are "R" and "r" for upper and lower case respectively.

See also

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• Raidô
• Я (Cyrillic Ya)
• Rho (Greek)

Latin letters

R | R | R | R | R | R | R | R | R | R | R | R | R | R | R | R | R | R | R | R | R | R | R (letter) | R | R | R | R | R | R | R (латиница) | R | R | R | R | R | R | R | R