What is the definition of a front in meteorology?

In meteorology, a front is precisely defined as a boundary zone between two air masses that have different temperatures, densities, and humidity levels. This boundary is significant because it is often where weather changes occur, leading to various phenomena such as precipitation, changes in wind direction, and shifts in temperature.

At this interface, the contrasting properties of the air masses can lead to complex interactions, including the formation of clouds and storms. Understanding fronts is crucial for predicting weather patterns and phenomena. Therefore, identifying them as boundary zones is foundational to the study of meteorology, as they are central to many weather systems and phenomena observed in the atmosphere. The other options do not accurately represent the concept of a front in meteorology, as they address different aspects of weather processes entirely.