R
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| ISO basic Latin alphabet |
|---|
| AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz |
R is the eighteenth letter of the Latin alphabet.
Semitic Rêš (the head) developed into Greek Ρ ῥῶ (Rhô) and Latin R. The Latin and Etruscan forms of the letter added an extra stroke to distinguish it from a later form of the Greek Pi.
See rhotic consonant, r-colored vowel, and guttural R for discussion of the family of 'r' sounds.
In typography, there was once a form called the half r, which was lost before the long s was.
In the International Phonetic Alphabet, 'r' represents the alveolar trill sound.
Romeo represents the letter R in the NATO phonetic alphabet. In international Morse code the letter R is DitDahDit: · - ·
Meanings for R
- In architecture, R-value is a non-SI measure of thermal resistance used in housing insulation.
- 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 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
- In driving a motor vehicle, R designates the reverse gear of a transmission
- In electrical engineering, R is often the variable 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 film The World Is Not Enough
- In music, R, also known as Rated R is a Queens of the Stone Age album.
- In financial securities, R is the stock symbol for Ryder Systems Inc.
- In geometry, r is often a variable for the radius of a circle
- In law, the abbreviation R. or R stands for either Rex (King) or Regina (Queen) depending on who is sitting on the throne 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.
- 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 real numbers
- In navigation, R denotes the relative direction "right"; see left and right
- In physics,
- R is the symbol for 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 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 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)
Pronunciation of R
| Alveolar trill /r/ | Listen | Template:Ll, Template:Ll, Template:Ll, Template:Ll, Template:Ll, Template:Ll, Template:Ll 'rr' |
| Alveolar approximant /ɹ/ | Listen | Template:Ll (most varieties) |
| Alveolar flap / Alveolar tap /ɾ/ | Listen | Template:Ll, Template:Ll, Template:Ll 'r', Template:Ll 'र' |
| Alveolar lateral flap /ɺ/ | Listen | Template:Ll |
| Retroflex flap /ɽ/ | Listen | Template:Ll, Template:Ll 'ड़', sometimes Scottish English |
| Voiced uvular fricative /ʁ/ | Listen | Template:Ll, Template:Ll, Template:Ll, Template:Ll, Template:Ll |
| Voiced velar fricative /ɣ/ | Listen | Template:Ll |