Places

• Mount Si, a mountain in state of Washington

• Si County, county in Anhui, China

• Si River, a river in China

• Slovenia, a European nation (esp. internet domain suffix and two-letter abbreviation)

• Solomon Islands, a Pacific island nation

• South India, a region in India

• Staten Island, a borough of New York City and an island in the Hudson River

• Province of Siena, an Italian province (two letter provincial designator)

Language

• ISO 639 alpha-2 code for the Sinhalese language

Computer science

• .si, the Internet country code top-level domain for Slovenia

• Shift In, a control code in the C0 control code set

• Swarm Intelligence, an artificial intelligence technique

• Synthetic Intelligence, an alternate term for or form of artificial intelligence

• Silicon Image Inc., a chip vendor

Education

• Saint Ignatius College Prepatory, a Jesuit college in the United States

• Samahang Ilokano, a fraternity/sorority based in the Philippines

• Seletar Institute, a defunct centralised institute in Singapore

• Silay Institute, Inc., a private college in the Philippines

• Smithsonian Institution, an American educational and research institute

Gaming

• Si, a self-replicating artifact in the computer game Ancient Domains of Mystery

• The Elder Scrolls IV: Shivering Isles, an expansion pack for The Elder Scrolls IV: Oblivion

• Sports Interactive, a British computer games development company

Mathematics and science

• Signal integrity, electronic circuit tools and techniques that ensure electrical signals are of sufficient quality for proper operation

• Si, the chemical symbol for silicon

• Si(x), the sinc function in mathematics

• Si, the sine integral in mathematics

• Survey of India, an Indian government agency responsible for managing geographical information about India

• International System of Units (Système International d'Unités), the modern international standard version of the metric system

• Simple Interest (Mathematics)

Medicine

• Sacroiliac, an anatomical abbreviation for the sacroiliac (joint)

• Self-injury

• Sensory integration, the neurological process that organizes sensation from one's own body and the environment

• * Upper often referring to Primary somatosensory cortex

• Sexual intercourse, a medical abbreviation

• Suicidal ideation, a medical term for thoughts about suicide

Music

• Si, the original name of the seventh note of solfege, later changed to "Ti"

• Sì (song), the name of the Italian entry to the Eurovision Song Contest 1974

• Sì (Carmen Russo song), the name of the 1985 song released by italian actress Carmen Russo

• Sí (album), an album by Mexican singer and songwriter Julieta Venegas

• Si, another name for the Sídhe, Celtic mythological beings

Government and politics

• Situationist International, a left-wing organisation

• Socialist International, a worldwide organisation of social democratic, labour, and democratic socialist political parties

• Sub-Inspector, a rank in Indian Police forces

• Survival International, a non-governmental indigenous rights organization

• Station Inspector, the highest non-commissioned rank in the Singapore Police Force

• Statutory Instrument, a form of delegated or secondary legislation in Great Britain

• Swedish Institute (Svenska institutet), a Swedish government agency which promotes Sweden abroad

• Sí or Solidarity and Equality, an Argentine political party

• Sitara-i-Imtiaz, an honourary award for civilians and the military in Pakistan

• Societas Iesu, the Jesuits, a religious order of the Roman Catholic Church

Sports

• SÍ Sørvágur, a Faroese sports association

• Sports Illustrated, an American sports magazine

Transportation

• IATA code for Skynet Airlines

• Reporting mark of Spokane International Railroad, a former railway in Washington, USA

• Spark-ignition engine

Miscellanea

• Si (surname) (姒), a Chinese surname used by kings in the Hsia Dynasty

• Honda Civic Si

• Sergeant Instructor, an appointment in the British Army

• Scouting Ireland, the national Scouting association of Ireland

• System integrator, a person or company that specializes in integrating systems

• Secret Invasion, a 2008 Marvel Comics event

• Superintendent (police), senior rank of British Police

• Short for the name Simon

See also

• S1