The amount of moisture present in the air is called which term?

• A. Absolute humidity
• B. Relative humidity
• C. Specific humidity
• D. Vapor pressure

Answer: (A)

The amount of moisture present in the air is described by absolute humidity. It measures the actual mass of water vapor per unit volume of air (commonly grams per cubic meter). This directly tells you how much moisture is there. Relative humidity, by contrast, is a percentage of saturation at a given temperature, so it tells how close the air is to holding all the water it can, not the actual amount. Specific humidity is the ratio of water vapor mass to total moist air mass, and vapor pressure is the pressure contribution of the water vapor. So for the raw quantity of moisture in a volume of air, absolute humidity is the correct term.