 A cloud would be, I guess, a concentration of gas and liquid droplets or solid particles. Generally, John, however, the term cloud is used to refer to the suspension of small ice or water particles in the atmosphere. And clouds in the atmosphere form whenever the relative humidity of an air mass reaches slightly more than, I think it's at 100%. And this can occur for a number of reasons. The upper motion of air, everybody knows that, which causes the expansion and cooling. Whoa! Whoa!