SI is the International System of Units. SI, Si, or si may also refer to:

Arts, entertainment, and media

Literature

* ''Si'' (novel), a 2014 novel by Bob Ong * ''Sí'' (Peruvian magazine), a magazine notable for its anti-corruption reporting * '' Skeptical Inquirer'', an American magazine covering topics on science and skepticism * ''

Sports Illustrated ''Sports Illustrated'' (''SI'') is an American sports magazine first published in August 1954. Founded by Stuart Scheftel, it was the first magazine with a circulation of over one million to win the National Magazine Award for General Excellen ...

'', an American sports magazine

Music

* ''Sí'' (Julieta Venegas album), released in 2003 * ''Sì'' (Andrea Bocelli album), released in 2018 * "Sí" (Martin Jensen song), a 2015 song * Si (musical note), the seventh note in the traditional fixed do solfège * ''Sì'' (operetta), an operetta by the Italian composer Pietro Mascagni * "Sì" (Gigliola Cinquetti song), the Italian entry to the Eurovision Song Contest 1974 * Si (Zaz song), 2013 * ''Sí'', a 2013 Spanish album by Malú * "Sì", a 1985 song released by Italian actress Carmen Russo

Other uses in arts, entertainment, and media

* ''Si'' (film), original title of the 2010 South Korean film ''Poetry''

Enterprises and organisations

Computing

* Swiss Informatics Society, a Swiss organization of computer science educators, researchers, and professionals * The SI, a former name of the American defense contractor Vencore

Education

* St. Ignatius College Preparatory, a Jesuit high school in San Francisco, California, US * Silay Institute, a private college in the Philippines

Government

* Si, a South Korean administrative unit * Survey of India, an Indian government agency responsible for managing geographical information * Swedish Institute (''Svenska institutet''), a Swedish government agency which promotes Sweden abroad

Politics

* Sarekat Islam, a socio-political organization in Indonesia under Dutch colonial rule * Catalan Solidarity for Independence, a Catalan political party *

Situationist International The Situationist International (SI) was an international organization of social revolutionaries made up of avant-garde artists, intellectuals, and political theorists. It was prominent in Europe from its formation in 1957 to its dissolution ...

, an organization of social revolutionaries *

Socialist International The Socialist International (SI) is a political international or worldwide organisation of political parties which seek to establish democratic socialism, consisting mostly of Social democracy, social democratic political parties and Labour mov ...

, a worldwide organization of political parties * Solidarity and Equality, an Argentine political party (Spanish: ''Solidaridad e Igualdad'')

Transportation

* Blue Islands (IATA airline code, SI) * Skynet Airlines (IATA airline code SI, ceased operating 2004) * Spokane International Railroad (reporting mark SI), a former railway in Washington, US

Other enterprises and organizations

* Samahang Ilokano, a fraternity/sorority based in the Philippines * SÍ Sørvágur, a Faroese sports association * Society of Indexers, a professional society based in the UK *

Sports Interactive Sports Interactive Limited is a British video game developer based in London, best known for the ''Football Manager'' series. Founded by brothers Collyer brothers (game designers), Oliver and Paul Collyer in July 1994, the studio was acquired in ...

, a British computer games development company

People with the name

* Si (surname), a Chinese surname * Si (given name) * Princess Si of Anding,first daughter of Wu zetain

Places

* Mount Si, a mountain in the U.S. state of Washington * Province of Siena (postal code and vehicle registration plate code) * Si County, Anhui, China * Si River, in China *

Slovenia Slovenia, officially the Republic of Slovenia, is a country in Central Europe. It borders Italy to the west, Austria to the north, Hungary to the northeast, Croatia to the south and southeast, and a short (46.6 km) coastline within the Adriati ...

's ISO 3166-2 code

Science and technology

Biology and healthcare

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums, Education center, education and Research institute, research centers, created by the Federal government of the United States, U.S. government "for the increase a ...

(SI is its international code) * Sacroiliac, an anatomical abbreviation for the sacroiliac (joint) * Self-injury, intentional, direct injuring * Shock index, a measurement used to determine if a person is suffering shock

Chemistry

* si, a chemical descriptor; See prochirality * Silicon, symbol Si, a chemical element * Disulfur diiodide, empirical formula SI

Computing and Internet

* .si, the Internet country code top-level domain for Slovenia * Shift In, an ASCII control character * SI register, or source index, in X86 computer architecture * Swarm intelligence, an artificial intelligence technique * Synthetic intelligence, an alternate term for or a form of artificial intelligence

Medical

* Suicidal ideation, thoughts of suicide * Self-injury, nonsuicidal injuring of the body

Motor vehicles

* Honda Civic Si, an automobile * Spark-ignition engine, a type of internal combustion engine

Other uses in science and technology

* Signal integrity, electronic circuit tools and techniques that ensure electrical signals are of sufficient quality * Sine integral, Si(x) * Spectral interferometry, attosecond physics technique

Titles and ranks

* Si, a Maghrebi Arabic variant of Sidi, a title of respect * Si, a variant of the Thai honorific Sri * Station inspector, a rank in the Singapore Police Force * Sub-inspector, a rank in Indian Police forces

Other uses

* Statutory instrument (UK), abbreviated SI, the principal form in which delegated legislation is made in Great Britain * Sì (dessert), a Chinese dessert * , , or , Celtic mythological beings * si, the

Sinhala language Sinhala ( ; Sinhala: , , ), sometimes called Sinhalese ( ), is an Indo-Aryan language primarily spoken by the Sinhalese people of Sri Lanka, who make up the largest ethnic group on the island, numbering about 16 million. It is also the first ...

ISO 639 alpha-2 code * Supplemental instruction, an academic support program often used in higher education