SAD
The initialism SAD may refer to:

Medicine
Schizoaffective disorder, a psychiatric diagnosis
Social anxiety disorder
Seasonal affective disorder, typically winter depression
Separation anxiety disorder in children
Sagittal abdominal diameter, body diameter at the waistline

Organisations
Political or military
Shiromani Akali Dal, a political party in India
Special Activities Division of the US Central Intelligence Agency, now named the Special Activities Center
Saraya Awliya al-Dam, an Iraqi militia

Sports clubs
Sociedad Anónima Deportiva, a type of incorporated sports club in Spain
Sociedade Anónima Desportiva, a type of incorporated sports club in Portugal

Science and technology
Selected area diffraction, a crystallographic experimental technique
Sum of absolute differences, in digital image processing
Single-wavelength anomalous dispersion, in X-ray crystallography

Transportation
Sandwell & Dudley railway station, with the station code SAD
Safford Regional Airport, Arizona, US, with the IATA airport code SAD

Songs
"S.A.D.", from Man Overboard's 2013 album Heart Attack

Other uses
Singles Awareness Day, a humorous holiday every February 14
The Single Administrative Document, EU customs form
The Suicide Attack Database, now named the Database on Suicide Attacks
The Standard American Diet, another name for the Western pattern diet

See also
Sad (disambiguation)