Final answer:
A diuretic is a compound that increases urine output and decreases water conservation by the body. Alcohol and caffeine act as diuretics by affecting the release of antidiuretic hormone.
Step-by-step explanation:
A diuretic is a compound that increases urine output and decreases water conservation in the body. It is used to treat hypertension, congestive heart failure, and fluid retention associated with menstruation. Alcohol and caffeine both act as diuretics, with alcohol inhibiting the release of antidiuretic hormone (ADH) and caffeine promoting vasodilation in the nephron. In the case of water, it is not a diuretic.