water cycle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The continuous process by which water is circulated throughout the earth and the atmosphere through evaporation, condensation, precipitation, and the transpiration of plants and animals.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The natural cycle of evaporation of water from the oceans etc, and subsequent condensation and precipitation as rain and snow