What does the term 'humidity' refer to?

The term 'humidity' specifically refers to the amount of moisture present in the atmosphere. This moisture can exist in various forms, such as water vapor, which is invisible, as well as in droplets like those seen in clouds or fog. Humidity is an important factor in meteorology because it affects weather patterns, precipitation, and temperature perceptions. For instance, high humidity can make temperatures feel warmer than they actually are, while low humidity can lead to cooler sensations.

The other options involve different meteorological concepts, such as temperature measurements, air density, and wind speed, which do not directly relate to the definition of humidity. Thus, the understanding of humidity is crucial for grasping various weather phenomena and forecasts.