Plain English Meaning

Water in the air. It can be an invisible gas, tiny liquid drops, or frozen crystals, depending on temperature and conditions.

Full Definition

Water present in the atmosphere, existing in any of three states: invisible water vapor (a gas), liquid droplets (clouds, rain, drizzle), or solid ice crystals (snow, hail, ice fog). The amount of moisture in the air at any time depends on temperature, since warmer air can hold more water vapor than colder air.

Context Anchor

Seen in aviation weather discussions when explaining clouds, fog, rain, snow, visibility, and ice on the aircraft.