Plain English Meaning
When water in the air turns into tiny droplets of liquid water -- like the moisture that forms on the inside of a cold drink glass on a warm day.
Full Definition
The process by which water vapor in the air changes into liquid water, typically when warm, moist air contacts a cooler surface or when the air itself cools below its dew point.
Context Anchor
Seen in fuel system discussions, especially when explaining how water can get into fuel tanks before flight.
Derivation
From the Latin condensare, meaning 'to make thick or dense.' Water vapor (a thin, spread-out ) becomes denser liquid water when it condenses -- the molecules pack together.