Si or si or SI may stand for:
'SI ' , the Système International d'Unités (the 'metric' International System of Units) one of two Spanish words pronounced like "see": sí (accented) for "yes " and si (unaccented) for "if " in music, Si , the seventh note of solfege in chemistry, Si , the chemical symbol for silicon in Mohican mythology , Si , the lunar deity Sinhalese language , (ISO 639 alpha-2) Slovenia (ISO 3166-1 alpha-2 country code , SI ) in UK law, a statutory instrument Smithsonian Institution Socialist International Sports Illustrated Sports Interactive Situationist International Staten Island, a borough of New York City and an island in the Hudson River Swedish Institute (Svenska institutet ) Supplemental Instruction Sexual Intercourse (medical abbreviation, not common usage) Self-injury or self-harm SI is the acronym for Swarm Intelligence In Mathematics si or Si is the Sine integral the IATA code for Skynet Airlines The Si is a self-duplicating artifact in ADOM This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. If an article link referred you here, you might want to go back and fix it to point directly to the intended page.