RI

RI or Ri may refer to:

Arts and media

• Ri, an augmented second in Solfege, in music education
• Ri, a representation of the second Swara in Indian classical music
• Russia Insider, a news website

Businesses and organizations

• Raffles Institution, a school in Singapore
• Refugees International, an international humanitarian organization
• Rehabilitation International, an international disability rights organization
• Rotary International
• Royal Institution of Great Britain
• Royal Institute of Painters in Water Colours, a society in the Federation of British Artists
• Chicago, Rock Island and Pacific Railroad (reporting mark RI)
• Mandala Airlines (IATA airline designator RI)

Language

• Rí, an ancient Gaelic word meaning "king"
• Ri (kana), a Romanization of the Japanese kana り and リ
• Ri, a proposed gender-neutral pronoun for Gender reform in Esperanto
• Indonesian language

Places

• Ri (administrative division), an administrative unit in both North Korea and South Korea
• Ri, Orne, a commune of the Orne département, in France
• Republic of Indonesia
• Rhode Island, US (postal abbreviation RI)

Science, technology, and mathematics

• Referential integrity, a database concept
• Refractive index of an optical medium (in physics/optics) is a number that describes how light propagates through that medium
• Arterial resistivity index
• Ring Indicator, a signal in the RS232 serial communications standard
• Rhombicosahedron, a polyhedron, by Bowers acronym

Other uses

• Ri, a common Korean surname (a variant of Lee)
• Rex Imperator or Regina Imperatrix, a suffix used by British monarchs as Emperors of India
• Ri, a unit of measurement in Japan and Korea

See also

• Isaac ben Samuel or the Ri ha-Zaken, a 12th-century French tosafist and Biblical commentator