Definition
Tiny liquid water particles suspended in the air that together form a visible cloud. Individual droplets are very small (typically a few to a few tens of microns across) and remain airborne because their size keeps them aloft on rising air. In below-freezing temperatures, cloud droplets can exist as supercooled liquid water that freezes on contact with an aircraft, producing structural icing.
Plain English
The microscopic water drops that make up a cloud. They are small enough to float in the air, and when they are colder than freezing they can freeze onto an aircraft when it flies through them.
Context Anchor
Seen in icing discussions, especially when explaining why an aircraft can pick up ice while flying through a visible cloud.
Derivation
Droplet combines drop with -let, a suffix meaning small. That helps here because cloud droplets are very small drops of water, not large raindrops, and their small size allows them to remain in the cloud air.
Why Pilots Care
These droplets freeze instantly on contact with an aircraft and build ice that reduces lift and increases drag.
Grounding Statement
A cloud is not a fog of vapor; it is a vast field of tiny liquid water drops, each small enough to drift on the air.
Intuition Check
Do not assume a cloud is only water vapor. In this context, cloud droplets are actual tiny liquid water drops, and some can remain liquid below freezing until they hit the airplane.
Example Sentence 1
Flying through a layer of supercooled cloud droplets at minus five degrees Celsius, the pilot quickly noticed rime ice forming on the wing leading edges.
Example Sentence 2
Clear ice formed when larger cloud droplets struck the leading edges during the flight.