SID

SID may refer to:

Amilcar Cabral International Airport, Sal Island, Cape Verde
Saab Information Display in most Saab automobiles built since 1994
Sensory integration dysfunction
Sports information director, a position title similar to PR Director or Press Secretary, usually within university/school systems' athletic departments
Status-income disequilibrium, a political term
Standard Instrument Departure at airports, also referred to as "Departure Procedure" (DP)
Strength in Democracy, a Canadian political party
Sudden Ionospheric Disturbance
Special Improvement District, commonly referred to as a "Business Improvement District"

In fiction

Space Intruder Detector, an early-warning satellite in the British television series UFO

MOS Technology SID, the Sound Interface Device (built-in sound chip) used in the Commodore CBM-II, Commodore 64 and Commodore 128 home computers
Seamless Image Database, see MrSID
Security Identifier, a unique alphanumeric character string assigned by a Microsoft Windows Domain controller
Service ID, used in Digital Video Broadcasting (DVB)
Session ID in computer science
Silence Insertion Descriptor, a special frame in VOIP audio codecs to enable comfort noise
NGOSS Shared Information/Data Model, later known as Information Framework (Frameworx), definition of NGOSS's common information model
Slew-induced distortion
A story identifier which uniquely identifies an article in Slash (weblog system)-based sites, such as Slashdot
Surface-induced dissociation, a method for fragmenting molecular ions in mass spectrometry
System identification number, identifier in wireless telephony of an analog, TDMA or CDMA system
System Identifier, an element of Oracle databases
.sid file extension:
- Audio file of Commodore 64, PSID and RSID sound file formats by MOS Technology SID
- Backup of a Steam playgame
- Compressed image file of LizardTech MrSID Image

SID (Latin: semel in die), meaning "once a day". Used only in veterinary medicine in contrast to quaque die (QD) meaning "each day".
mSin3 interaction domain, a transcriptional repressor domain
Source to image-receptor distance, a measurement in clinical radiology describing the distance between a radiation source and the detector
"Strong Ion Difference" (according to Peter A. Stewart)

The Scientific Investigation Division of the Los Angeles Police Department
Security and Intelligence Division, Singapore's foreign intelligence service
Servizio Informazioni Difesa, Italian military secret service from 1965 to 1977 (replaced by the SISMI)
Služba za istrage i dokumentaciju, the Serbian Service for Investigations and Documentation
Society for Information Display, a professional society dedicated to the study of the physics and engineering of display devices
Society for International Development, a professional society for members of the international-development community.
Sport-Informations-Dienst (Sport Information Service), founded 1945 in Germany, a sport media service