In the fields of psychology and psychiatry, the terms depression or depressed refer to sadness and other related emotions and behaviors. It can be thought of as either a disease or a syndrome.

The Diagnostic and Statistical Manual of Mental Disorders (DSM) states that a depressed mood is often reported as feeling sad, helpless, and hopeless. In traditional colloquy, “depressed” is often synonymous with “sad,” but both clinical and non-clinical depression can also refer to a conglomeration of more than one feeling.