Answer: In moist air, the mass of water vapor contained in 1 kg of dry air is called the "moisture content" of moist air, which is often expressed by ω. The moisture content ω is almost proportional to the partial pressure of water vapor 
,and inversely proportional to the total air pressure p. ω accurately reflects the amount of water vapor contained in the air. If the atmospheric pressure remains unchanged, then when the temperature of moist air is constant, is also constant. At this time, the relative humidity increases, its moisture content increases, and its hygroscopic capacity decreases.
