Dew, layer of water droplets that forms at night on or near the ground. Dew may form in two ways: First, water vapor may rise out of the ground by capillary action and form droplets on reaching cooler surfaces (leaves, rocks) near ground level. Second, and more commonly, moisture from the air may condense in contact with relatively cool objects. In arid and semiarid areas, dew is an important source of moisture for plants.
21st Century Webster's Family Encyclopedia21st Century Webster's Family Encyclopedia - Davis, Henry Gassaway to Diamond