R is the eighteenth letter of the Latin alphabet.
Semitic Rêš (the head) developed into Greek Ρω (Rô). The sound value /r/ however was maintained in Greek as well as Etruscan and Latin. The finishing stroke was added to the Greek Rho to distinguish it from a later form of the Greek Pi, at a time when there were only capital letters in Latin. It is usually one of the liquid consonants, though there are many ways it is pronounced in European languages.
Romeo represents the letter R in the NATO phonetic alphabet.
Meanings for R
- 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,
- 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,
- 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); see R (rating)
- 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, R. stands for Rex (king) or Regina (queen) in court citations in countries that recognize the British monarch as head of state
- In mathematics,
- 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)
- 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,
Two-letter combinations starting with R:
Letter-digit combinations starting with R: