| Term | Definition |
| water cycle | the continuous cycle of water as it changes between 3 states: liquid, gas, and solid |
| energy | the amount of movement the water molecules have |
| evaporation | when water changes from a liquid into a gas |
| condensation | when water vapor cools and changes from a gas into a liquid |
| precipitation | when water droplets combine and become heavier than air, then fall to the earth as rain, snow, sleet, or hail |
| transpiration | when plants release moisture into the atmosphere |
| surface runoff | after precipitation travels downhill, it appears in lakes, rivers |
| water table | the level of the water under ground |
| ground water | the water that has been absorbed ito the earth |