HYDROLOGIC CYCLE: The natural sequence through which water passes into the atmosphere as water vapor, precipitates to earth in liquid or solid form, and ultimately returns to the atmosphere through evaporation.

EVAPORATION: The changing of a liquid into a gas, often under the influence of heat.

CONDENSATION: The process by which atmospheric water vapor liquefies to form fog, clouds, or the like, or solidifies to form snow or hail.

PRECIPITATION: Falling products of condensation in the atmosphere, as rain, snow, or hail.

Water that is accumulated or collected.

RUNOFF: Something that drains or flows off, as rain that flows off from the land in streams.

INFILTRATION: The seepage of water into soil or rock.

the process of the absorption of water by plants, usually through the roots, the movement of water through plants, and the loss of the water to the atmosphere through small openings on the underside of leaves called stomata. Transpiration is one of the processes that scientists rely on when phytoremediation is used to clean up contaminated ground water.