Which type of humidity measurement indicates the amount of water vapor in the air?

Absolute humidity is the measurement that directly indicates the amount of water vapor present in the air, expressed as the mass of water vapor per unit volume of air. This measurement provides a straightforward quantification of moisture content, making it particularly useful for understanding how much water vapor is in the atmosphere at a given temperature and pressure.

Contrasting with absolute humidity, relative humidity refers to the percentage of moisture in the air relative to the maximum amount of moisture that the air can hold at a specific temperature. Specific humidity measures the mass of water vapor per unit mass of air (including the water vapor), while the dew point represents the temperature at which air becomes saturated with moisture, leading to condensation. Each of these measurements serves a unique purpose in studying atmospheric moisture, but absolute humidity is the direct indicator of the quantity of water vapor itself.