Water on earth is used over and over. The water cycle, the continuous movement of water from ocean to air and land then back to the ocean in a cyclic pattern, is a central concept in meteorology. In the water cycle, the sun heats the Earth's surface water, causing that surface water to evaporate (gas). This water vapor then rises into the earth's atmosphere where it cools and condenses into liquid droplets. These droplets combine and grow until they become too heavy and fall to the earth as precipitation (liquid if rain, solid if snow).
Water is temporarily stored in lakes, glaciers, underground, or living organisms. The water can move from these places by streams and rivers, returns to the oceans, is used by plants or animals or is evaporated directly back into the atmosphere.
