posted by Anonymous .
When air is saturated,
the relative humidity is 100%,
the air is holding the max. amt. of moisture, and
condensation can occur.
Correct except for the "the air is holding the max. amt. of moisture" part. This would be true if you always had thermodynamical equilibrium. You can cool air well below its dew point without condensation occuring. So the relative humidity can, strange as it sounds, exceed 100%.
You need impurities for small water droplets to form. Water vapor can be supercooled, it is then in the wrong phase. The Gibbs free energy is then in some local minimum, the global minimum is the the water phase....