Aquifer: underground layer of permeable rock, from which groundwater can be easily extracted using a well.

Condensation: water changes from a gas to a liquid.

Condensation nuclei: particles of dust, pollen, salt, ice, etc. around which water vapor condenses

Evaporation: water changes to water vapor

Evapotranspiration: evaporation + transpiration

Groundwater: water stored underground, in the pore spaces of rocks and soil

Humidity: measure of the amount of water vapor in the air

Infiltration: water that seeps into the soil and can become groundwater

Precipitation: water falls to Earth as rain, snow, sleet, hail, etc.

Reservoir: place where water is stored

Residence Time: amount of time a water molecule will stay in one reservoir

Runoff: water on the surface of earth that does not infiltrate the ground

Transpiration: liquid water from the leaves of plants changes to water vapor

Water Table: top surface of groundwater