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Clinical depression, a medical condition identified by clusters of symptoms such as markedly-decreased mood, motivation, interest, energy levels, etc (also known as severe depression disorder or major depression disorder).

Depression (mood), an everyday term for a sad or low mood or the loss of pleasure.

Depression (geology), a sunken geological formation.

Depression (economics), a longer-lasting and more severe economic downturn than a recession.

The Great Depression, a severe economic recession in the 1930s.

Depression (meteorology), an area of low atmospheric pressure associated with cyclones and weather fronts.

Depression (physiology), a lowering, in particular a reduction in a particular biological variable or the function of an organ, contrasted to elevation.