What term is used to describe the difference between the air temperature and dew point temperature?

The term "spread" is correctly used to describe the difference between the air temperature and dew point temperature. In meteorology, this spread indicates the gap between how warm the air is (the air temperature) and how much moisture is present in the air (the dew point). A larger spread generally suggests drier air, as the air temperature is significantly higher than the dew point, while a smaller spread indicates more moisture and can lead to conditions favorable for cloud formation or fog.

In practice, this concept is crucial for aviation, particularly for understanding weather conditions that may affect flight operations. For example, when the spread is small, pilots and air traffic controllers may be more alert to the potential for reduced visibility due to fog, as the air is close to saturation.

The other options do not accurately describe this specific meteorological concept. Terms like "humidity gap," "temperature spread," and "condensation difference" are not standard meteorological terminology for the difference between air temperature and dew point temperature. Thus, "spread" is the precise and correct term used in this context.