How is relative humidity expressed mathematically?

Relative humidity is a measure of the current amount of water vapor in the air compared to the maximum amount of water vapor that the air can hold at a specific temperature, expressed as a percentage. Mathematically, relative humidity is defined as the ratio of the actual vapor density (the amount of moisture present in the air) to the saturation vapor density (the maximum amount of moisture the air can hold at that temperature) multiplied by 100 to convert it into a percentage format.

This relationship indicates how close the air is to being saturated with moisture. If the actual vapor density equals the saturation vapor density, relative humidity will be 100%, indicating that the air is fully saturated and unable to hold any more water vapor, which often leads to condensation and the formation of clouds or precipitation. Conversely, a lower percentage indicates drier air.

The other options do not accurately represent how relative humidity is calculated and therefore do not contribute to the correct understanding of the concept.