Hidden Agenda,
I think what crab was saying was that the mechanism for forming fog (ie cooling of air until it is completely saturated and moisture becomes visible) is the same as that for forming cloud (ie cooling of air [by a lifting mechanism which cools it because of the reduction in pressure and the change of temperature with altitude] until it is completely saturated and moisture becomes visible).
The same basic requirements need to be met:
cooling;
moisture;
nucleii to condense onto.
The point of mine that I was clarifying is that the result is the same but the manner in which the cooling occurs is slightly different.
Sorry for the confusion.
CB