RR 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.
Romeo represents the letter R in the NATO phonetic alphabet.
R is also:
- In organic chemistry, the symbol for the hydrocarbon chain.
- A rating given for films given by the Motion Picture Association of America, see R (rating)
- The stock symbol for Ryder Systems Inc
- A statistical programming language; see R (programming language)
- The symbol used to represent the set of real numbers. Commonly displayed in the blackboard bold font.
- The variable R for electrical resistance
- The variable r for radius of a circle
- Symbol for roentgen
Two-letter combinations starting with R: