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
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