What term describes the ratio of actual water vapor present in the atmosphere to the amount that would be present if the air were saturated?

Relative humidity is the term used to describe the ratio of the actual amount of water vapor present in the atmosphere to the amount that would be present if the air were saturated, expressed as a percentage. This measurement indicates how close the air is to being fully saturated with moisture.

When relative humidity is at 100%, it means the air is fully saturated, and no additional moisture can be held without condensation occurring. Values below 100% indicate that the air can hold more moisture. Understanding relative humidity is crucial for meteorology, as it affects weather patterns, temperature perception, and the likelihood of precipitation.

Other terms like absolute humidity refer to the actual mass of water vapor in a given volume of air, without considering whether the air is saturated. Vapor pressure refers to the pressure exerted by the water vapor present in the air. The saturation point indicates the maximum amount of water vapor that air can hold at a specific temperature, but it does not convey the ratio of actual moisture to potential moisture as relative humidity does.