The word sad refers to an emotional condition, the antonym of "happy". Sadness is often associated with depression, suffering or grief..

SAD is a three letter acronym.

Sagittal Abdominal Diameter, a medical term

Schizoaffective disorder

Seasonal affective disorder

Sexual arousal disorder

Shiromani Akali Dal, an Indian political party

Silicon Avalanche Diode, an electronic component

Singles Awareness Day

Small angle diffraction, a technique for analysing materials

Social anxiety disorder

Special Activities Division, the Central Intelligence Agency's special operations force

Standard American Diet

Sum of absolute differences, a simple metric for motion estimation in video compression

Supine Abdominal Height, a medical term

Systems Analysis and Design

Sad can also mean:

Ṣād, a letter of the Arabic alphabet (ﺹ).

Sad, the 38th sura of the Qur'an (named after the letter)

Sad, urban-type settlement in Dnipropetrovsk Oblast, Ukraine