What is the difference between relative humidity and absolute humidity?

Relative humidity and absolute humidity are both important concepts in understanding moisture content in the air, but they measure different aspects of humidity. The correct choice highlights that relative humidity refers to the amount of moisture in the air compared to the maximum amount of moisture the air can hold at a given temperature, expressed as a percentage. This means relative humidity changes with temperature; warm air can hold more moisture than cold air, hence the capacity is variable.

On the other hand, absolute humidity quantifies the total mass of water vapor present in a specified volume of air, regardless of temperature. It is a measure of the actual amount of water vapor available in the air, typically expressed in grams of water per cubic meter of air.

Understanding this distinction is crucial for applications in meteorology, HVAC design, and other fields involving environmental control, as it affects comfort levels and how moisture affects materials and structures. The other options do not accurately represent the definitions or relationships between these two measures of humidity.