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, an American sports magazine Soccer International, an Australian monthly 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 Stark Industries, a fictional company appearing in comic books published by Marvel Comics
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, an organization of social revolutionaries Socialist International, 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, 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 Si (ancient Seeia/Seia), northern Hauran (ancient Auranitis), Syria; archaeological site with Nabataean temples, necropolis Province of Siena (postal code and vehicle registration plate code) Si County, Anhui, China Si River, in China Slovenia's ISO 3166-2 code Staten Island (SI), one of the burroughs of New York City Sukabumi railway station (SI), a railway station in Sukabumi, Indonesia
Science and technology
Biology and healthcare Smithsonian Institution (SI is its international code) Sacroiliac, an anatomical abbreviation for the sacroiliac (joint) Self-incompatibility, any genetic mechanism that prevents self-fertilization in hermaphroditic organisms Self-injury, intentional, direct injuring Sucrase-isomaltase, encoded by the SI gene Suicidal ideation, thoughts of suicide 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 Superintelligence Swarm intelligence, an artificial intelligence technique Synthetic intelligence, an alternate term for or a form of artificial intelligence
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 Systems integrator, in engineering
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 ISO 639 alpha-2 code Supplemental instruction, an academic support program often used in higher education
See also See (disambiguation) Sea (disambiguation) SL (disambiguation) S1 (disambiguation)