What is the temperature at which water vapor begins to deposit as a liquid?

The temperature at which water vapor begins to deposit as a liquid is known as the dew point. This is the temperature at which the air becomes saturated with moisture, leading to condensation of water vapor. As the air cools to this specific temperature, it can no longer hold all of the moisture in the form of vapor, so the water vapor begins to change back into liquid water, forming dew. Understanding the dew point is crucial in various fields, including meteorology and HVAC, as it helps predict weather conditions and manage humidity levels for comfort and equipment efficiency.

Other terms provided, such as boiling point, melting point, and freezing point, refer to different phase changes of water: the boiling point is when water turns to vapor, the melting point refers to the transition from solid ice to liquid water, and the freezing point is when liquid water turns into solid ice. These points do not pertain to the condensation of water vapor back into liquid water, which is why they are not applicable in this context.