mmHg, or millimeters of mercury, is a unit of pressure commonly used in medicine and meteorology. It measures how high a column of mercury rises in a tube when pressure is applied. This unit is particularly important in measuring blood pressure, where it indicates the force of blood against the walls of arteries. In a clinical setting, blood pressure readings are expressed in mmHg, such as 120/80 mmHg. The first number represents systolic pressure, the pressure during heartbeats, while the second number indicates diastolic pressure, the pressure when the heart is at rest. Understanding mmHg helps in assessing cardiovascular health.