SAD

The word sad refers to an emotional condition; see sadness or the Wiktionary entry for more.

The acronym SAD may refer to: Sagittal Abdominal Diameter, the diameter around one's waistline
Schizoaffective disorder, a psychiatric diagnosis with symptoms of a mood disorder and schizophrenia
Seasonal affective disorder, a mood disorder with depressive symptoms in the winter
Separation anxiety disorder, a psychological condition related to anxiety of separation from home or from people
Sexual arousal disorder, the inability to attain or maintain typical responses to sexual arousal
Selected area diffraction, a crystallographic experimental technique that can be performed inside a transmission electron microscope
Shiromani Akali Dal, an Indian political party
Silicon Avalanche Diode, an electronic component
Singles Awareness Day, a humorous holiday celebrated on February 14
Social anxiety disorder, a diagnosis referring to excessive anxiety in social situations
Special Activities Division, the Central Intelligence Agency's special operations force in the United States
Standard American Diet, a phrase associated with diet-related obesity in the United States
Sum of absolute differences, a simple metric for motion estimation in video compression
Syncope, Angina, and Dyspnea, classic symptoms of severe aortic stenosis
Systems Analysis and Design, an interdisciplinary part of science
SAD (public transport), an Italian transportation company (Italian: SAD (Bolzano))

Sad can also mean: Ṣād, a letter of the Arabic alphabet (ﺹ).
Sad (sura), the 38th sura of the Qur'an (named after the letter)
Sad, Podlaskie Voivodeship (north-east Poland)
Sandawe language (ISO 639 language code), a tonal language spoken in Tanzania

Translation

The word "SAD" occurs as such in the following languages: English, German, Esperanto, French, Italian, Japanese, Polish, Slovak, Swedish.

Translation in Ripuarian: SAD (Watt ėßß datt?).