What is the term for the amount of moisture in the air compared to the amount the air can hold at saturation?

Relative humidity is defined as the ratio of the current amount of moisture in the air to the maximum amount of moisture the air can hold at a specific temperature before it becomes saturated. It is expressed as a percentage. This measure gives insight into how much water vapor is present in the air compared to what the air can potentially hold at saturation. For example, if the air is holding half of the maximum moisture it can contain, the relative humidity would be 50%.

This concept is crucial in various contexts, including weather forecasting, HVAC systems, and understanding human comfort levels and health implications related to moisture in the atmosphere. By using relative humidity, we can make more informed predictions about weather conditions, assess potential for condensation or mold growth, and optimize indoor climate control systems.