Alan Lazerow of Frederick and his co-workers have been wondering: "What is cloudier: 'cloudy' or 'mostly cloudy'? ... 'Partly sunny' or 'partly cloudy'?" Pay attention, class: There are no such words as "mostly" or "sunny" in the American Meteorological Society's Glossary. It says "cloudy" means at least 70 percent cloud cover, while "partly cloudy" means 30 percent to 60 percent cloud cover. "Clear" means a maximum cloud cover of 20 percent. Anything else is a personality test. Is your TV meteorologist's sky half-full? Or half-empty?