What is absolute humidity?

Absolute humidity is defined as the actual amount of water vapor present in a specified volume of air, typically expressed in grams of water vapor per cubic meter of air. This measurement gives a direct quantity of moisture in the air regardless of temperature or pressure, which distinguishes it from other humidity concepts. It reflects the real density of water vapor in the air, providing essential information for understanding atmospheric conditions, weather patterns, and processes related to aircraft performance and efficiency.

In contrast, other options focus on related but different concepts of moisture and air composition. For example, the maximum amount of water vapor refers to a saturation point, rather than the actual measured quantity. The temperature of saturated air relates to the point at which air can no longer hold additional moisture, and the pressure of water vapor involves how much pressure the water vapor exerts within that air mixture, neither of which define absolute humidity itself.