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

Latin alphabet Aa Bb Cc Dd Ee Ff Gg Hh Ii Jj Kk Ll Mm Nn Oo Pp Qq Rr Ss Tt Uu Vv Ww Xx Yy Zz

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

Contents 1 History 1.1 Minuscule 2 Various phonetic realizations of R 3 Meanings for R 4 Codes for computing 5 See also

History

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

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 ῥῶ (Rhô) and Latin R. It is likely that some Etruscan and Western Greek 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.

Various phonetic realizations of R

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. Other languages may use the letter r in their alphabets (or latin transliterations schemes) to represent rhotic consonants different from the alveolar trill.

Alveolar trill /r/	Listen	Arabic, Armenian, British English (in emphatic speech), Finnish, German in performance arts, Hungarian, Italian, Polish, Portuguese, Romanian, Scots, Spanish 'rr'
Alveolar approximant /ɹ/	Listen	English (most varieties)
Alveolar flap / Alveolar tap /ɾ/	Listen	Greek, Hindi 'र', Portuguese, Spanish 'r', Turkish
Alveolar lateral flap /ɺ/	Listen	Japanese
Retroflex approximant /ɻ/	Listen	most varieties of American English
Retroflex flap /ɽ/	Listen	Hindi 'ड़', Norwegian, sometimes Scottish English
Uvular trill /ʀ/	Listen	French; German; some dialects of Dutch, Italian and Swedish
Voiced uvular fricative /ʁ/	Listen	Danish, Dutch, French, German, Hebrew

Meanings for R

• In architecture, R-value is a non-SI measure of thermal resistance used in housing insulation.
• In astronomy,
  • R stands for an orangish class of stars, K carbon stars.
  • 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 sometimes 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 an environment for statistical computing 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 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 p < q < r.
  • An R-value is the expression on the right-hand-side of an inequality statement.
• A Spanish Telecomunications Company called R.
• 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 an environment for statistical computing 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

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 "&#82;" and "&#114;" for upper and lower case respectively.

See also

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

Two-letter combinations Ra Rb Rc Rd Re Rf Rg Rh Ri Rj Rk Rl Rm Rn Ro Rp Rq Rr Rs Rt Ru Rv Rw Rx Ry Rz RA RB RC RD RE RF RG RH RI RJ RK RL RM RN RO RP RQ RR RS RT RU RV RW RX RY RZ Letter-digit & Digit-letter combinations R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 0R 1R 2R 3R 4R 5R 6R 7R 8R 9R

The Letter "R"
General:	The letter R · Rhotic consonants (R-like sounds) · Rhotic and non-rhotic accents · R-colored vowels · Guttural R · Linking R and Intrusive R
Pronunciations:	Alveolar trill [r] · Alveolar approximant [ɹ] · Alveolar flap / Alveolar tap [ɾ] · Alveolar lateral flap [ɺ] ·Retroflex approximant [ɻ] · Retroflex flap [ɽ] ·Uvular trill [ʀ] ·Voiced uvular fricative [ʁ]
Variations:	 (R rotunda) · Ɍɍ (R with stroke) · Ȑȑ · Ŕŕ · Ŗŗ · Řř · Ȓȓ · Ṙṙ · Ṛṛ · Ṝṝ · Ṟṟ · Rd rd · Rh rh · Rl rl · Rn rn · Rr rr · Rt rt · Rnd rnd · ᚱ (Raidô) · ℛ (Riemann integral) · ℜ (Real part) · ℝ (Real number) · ® (Trademark) · Ⓡ (Enclosed R)