What is the term for the boundary between two air masses?

The term for the boundary between two air masses is known as a front. In meteorology, a front is a zone that separates differing air masses having distinct temperature and moisture characteristics. This boundary plays a crucial role in weather patterns and phenomena, as it is often where precipitation, storms, and severe weather occur. Fronts are classified into several types, such as warm fronts, cold fronts, stationary fronts, and occluded fronts, each describing the interaction between the air masses involved and the resulting weather conditions.

On the other hand, an air mass refers to a large body of air that has uniform temperature and humidity properties; it does not denote a boundary. The term boundary layer typically refers to the lowest part of the atmosphere, where the Earth's surface significantly influences the flow of air above it, rather than a boundary between two distinct air masses. Surface level denotes a specific altitude or reference point from which weather phenomena are measured but does not describe the interaction between air masses. Therefore, the concept of a front distinctly identifies the interface where different air masses meet and interact.