Which term describes the amount of moisture the air can hold at a certain temperature?

The correct term that describes the amount of moisture the air can hold at a certain temperature is saturation vapor pressure. This term specifically refers to the maximum pressure of water vapor that can exist in the air at a given temperature. As temperature increases, the capacity of air to hold moisture also increases, meaning that the saturation vapor pressure will be higher in warmer conditions.

Absolute humidity measures the actual amount of water vapor in the air, usually expressed in grams per cubic meter, but does not provide insights into how much moisture the air can hold relative to its current temperature. Relative humidity, on the other hand, is a percentage that indicates how close the amount of moisture in the air is to saturation but does not directly describe the capacity of air to hold moisture at a specific temperature. The dew point is the temperature at which air becomes saturated and water vapor begins to condense, but it is not a direct measure of the air's capacity to hold moisture. Therefore, saturation vapor pressure is the most accurate term to describe the moisture-holding capacity of air at a given temperature.