Si

Si, si, or SI may refer to (all SI unless otherwise stated):

Measurement, mathematics and science

• International System of Units (Système international d'unités), the modern international standard version of the metric system
• 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 sine integral in mathematics
• Survey of India, an Indian government agency responsible for managing geographical information about India
• 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
• Structural Integration, a form of bodywork, coined by Dr Ida Rolf

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
• Southern Ireland, a former constituent country of the UK now officially known as the Republic of Ireland
• 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
• Si Thai: ศรี Sri

Computer science

• .si, the Internet country code top-level domain for Slovenia
• Systems integrator, an IT company that specializes in integrating complex computer or data systems from multiple vendors
• 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
• SI register, or source index, in X86 computer architecture

Education

• Saint Ignatius College Preparatory, 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
• Supplemental Instruction, an academic support program often used in higher education

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

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

• Catalan Solidarity for Independence, an independist Catalan political party
• Situationist International, a left-wing organisation
• Socialist International, a worldwide organization of democratic socialist and labour 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 honorary 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
• Honda Civic Si

Miscellanea

• Sí (Peruvian magazine), a magazine notable for its anti-corruption reporting
• Si (surname) (姒), a Chinese surname used by kings in the Xia Dynasty
• 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
• Superintendent (police), senior rank of British Police
• Poetry (film), a 2010 South Korean film with the original title Si (시)
• Short for the name Simon

See also

• S1 (disambiguation)