R (disambiguation)

R is the eighteenth letter of the Latin alphabet. It may also refer to:

* R (programming language), an environment for statistical computing and graphics
* IBM System R, an IBM database system
* R (complexity), the set of all recursive languages
* R-value (soils), property of soils used in pavement design
* "Rated R" (album), an album by "Queens of the Stone Age"
* "R." (album) (1998) by R. Kelly
* Mundo-R, a Spanish Telecommunications Company
* Rolled-R, the alveolar trill of Spanish, Italian, & Arabic languages
* R-value (insulation), a non-SI measure of thermal resistance used in housing insulation
* The three Rs of Reading, wRiting and aRithmetic
* The three Rs of Russell and Burch for the ethical use of animals in scientific procedures: Replace, Reduce, Refine
* The three Rs of the Waste hierarchy: of Reduce, Reuse and Recycle
* R (cross section ratio), the ratio of hadronic to muonic cross sections
* Röntgen is a unit of measurement for ionizing radiation (such as X-ray and gamma rays),

Chemistry

* In chemistry, the gas constant
* In a chemical formula or structrual formula, an unspecified group of atoms (denoting multiple possibilities exist)
* The R-# refrigerant numbering system

R may also refer to:
* Haplogroup R (mtDNA), a human mitochondrial DNA (mtDNA) haplogroup
* Haplogroup R (Y-DNA), a Y-chromosomal DNA (Y-DNA) haplogroup
* R, a stellar classification, for orangish or K carbon stars
* R, a film rating in the Motion Picture Association of America film rating system
* R, a character played by John Cleese in the James Bond film "The World Is Not Enough"
* R·Type, an arcade video game
* R with an enclosing circle, ®, denotes a registered trademark
* R, the symbol for the currency of South Africa, the Rand (currency)
* R, the symbol for the amino acid arginine
* R, Japan Radio Company's mobile phone of NTT DoCoMo in Japan
*r, the Pearson product-moment correlation coefficient
* R, the NYSE ticker symbol for Ryder

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