Definition
Visible masses of tiny water droplets, ice crystals, or both, suspended in the atmosphere. Clouds form when rising air cools to its dew point and water vapor condenses onto microscopic particles called condensation nuclei. The type, height, and shape of a cloud reveal what the atmosphere is doing — its stability, moisture content, and likely weather.
Plain English
Clouds are the visible bunches of water droplets or ice crystals you see in the sky. They form when moist air rises, cools, and the moisture turns from invisible vapor into tiny visible drops.
Context Anchor
Pilots encounter clouds in weather reports, forecasts, preflight planning, and in flight when deciding whether they can see enough to continue safely.
Derivation
From Old English clud, originally meaning 'a mass of rock or hill.' The word was later applied to the lumpy, hill-like shapes seen in the sky. The history is a useful reminder that pilots read clouds by their shape — what they look like tells you what the air is doing.
Why Pilots Care
Clouds indicate potential turbulence, icing, reduced visibility, or convective activity that directly affects flight safety and routing decisions.
Grounding Statement
When you see a cloud, you are seeing the exact altitude where rising air finally cooled enough for its moisture to become visible.
Intuition Check
Do not think of clouds as just scenery. For pilots, clouds are weather information: they show where moisture and cooling are present and can directly affect visibility and flight decisions.
Example Sentence 1
The pilot delayed departure because low clouds had reduced the ceiling below VFR minimums.
Example Sentence 2
Building cumulus clouds ahead prompted the pilot to divert around the area to avoid possible thunderstorms.