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
• or R, set of all real numbers
• 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)
• Rydberg constant, a physical constant relating to energy levels of electrons within atoms

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

This disambiguation page lists articles associated with the same Latin letter. If an internal link led you here, you may wish to change the link to point directly to the intended article.