What phenomenon occurs when the air cannot hold any more water vapor?

Saturation is the phenomenon that occurs when the air reaches its maximum capacity to hold water vapor. At this point, the air is fully saturated, meaning it cannot contain any additional moisture without the vapor beginning to condense into liquid water. This condition is influenced by temperature; warmer air can hold more moisture than cooler air. When saturation is achieved, the relative humidity reaches 100%, and any additional water vapor will lead to condensation, forming clouds or precipitation.

The other options refer to different processes in the water cycle. Condensation is the process that occurs when water vapor cools and transforms into liquid, typically happening when air cools after reaching saturation. Evaporation is the process by which liquid water changes into vapor, usually when the air is not saturated. Transpiration refers to the release of water vapor from plants into the atmosphere. These processes are interconnected but distinct from the state of saturation itself.