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Photo: Mary Hollinger, NOAA Biologist, NODC.


1. METEOROLOGY. In the atmosphere, the process by which water vapor turns into water or ice in the form of rain, snow, hail, sleet, dew, fog, or mist. Also, the water or ice that comes down as rain, snow, or hail, and the amount that is precipitated. For example, precipitation in many parts of the interior United States averages about 30 inches per year. 2. CHEMISTRY. The process by which a substance is separated out of a solution and settled to the bottom as a solid; the newly separated solid is called a precipitate. [Precipitation comes from a Latin word meaning “fall” or “headlong descent.”]