Definition
The condition of a substance, usually a gas or liquid, that contains the maximum amount of another substance it can hold at a given temperature and pressure. In aviation maintenance, the term is most often applied to air holding the maximum amount of water vapor it can carry, or to a fluid that has absorbed all of a dissolved substance it is able to hold.
Plain English
Completely full and unable to take in any more. The air, liquid, or material has reached its limit at the current temperature and pressure.
Context Anchor
Seen in weather, humidity, cloud, fog, dew, frost, and aircraft moisture discussions.
Derivation
From the Latin saturare, meaning 'to fill' or 'to glut.' The original sense of being filled to capacity carries directly into the technical meaning: a saturated substance cannot hold any more.
Why Pilots Care
Saturation drives real-world maintenance and flight decisions. Saturated air is at 100% relative humidity, which signals possible fog, visible moisture, or icing conditions. A saturated filter or absorbent material has stopped doing its job and must be replaced.
Analogy
Think of a kitchen sponge that has soaked up all the water it can hold. Add another drop and it just runs off. That sponge is saturated.
Grounding Statement
If moist air cools enough to become saturated, some of its invisible water vapor can turn into visible moisture such as fog, cloud, dew, frost, or ice.
Intuition Check
Saturated does not just mean “wet.” In aviation weather, it means the air is holding the maximum water vapor it can hold at its current temperature and pressure.
Example Sentence 1
When the air becomes saturated, water vapor begins to condense, forming dew, fog, or clouds.
Example Sentence 2
Mechanics watch for saturated conditions before engine start because they raise the risk of carburetor ice.