Which process involves water vapor turning into liquid water?

The process that involves water vapor turning into liquid water is condensation. This occurs when water vapor in the air cools and changes back into a liquid state, forming tiny droplets. This transformation can happen on surfaces like cool glass or in the atmosphere, leading to phenomena like the formation of clouds or dew.

In the context of atmospheric moisture, condensation is particularly significant because it is a key part of the water cycle, helping to create precipitation and contribute to weather patterns. The efficiency of this process is influenced by temperature and humidity; lower temperatures typically enhance condensation by reducing the capacity of air to hold moisture in vapor form.

Other processes such as evaporation (the transition from liquid to vapor), precipitation (the fall of water in liquid or solid form from the atmosphere), and sublimation (the direct transition from solid to vapor) do not represent the conversion of water vapor to liquid water and, therefore, do not fit the description given in the question.