| Hydrosphere | The sum of all water on a planet. |
| Hydrologic Cycle | The process by which water is continuously exchanged between earth's various water sources. |
| Transpiration | Evaporation of water from plants. |
| Condensation | The process by which a gas turns into a liquid. |
| Precipitation | Water falling from the atmosphere as rain, snow, sleet, or hail. |
| Distillation | Evaporation and condensation of a mixture to separate the mixture's individual components. |
| Residence Time | The average time a given particle will stay in a given system. |
| Salinity | A measure of the mass of dissolved salt in a given mass of water. |
| Firn | A dense ice pack of old snow. |
| Water Table | The line between the water-saturated soil and the soil that is not saturated with water. |
| Percolation | The process by which water moves downward in the soil, toward the water table. |
| Adiabatic Cooling | The cooling of a gas that happens when the gas expands with no way of getting more energy. |
| Cloud Condensation Nuclei | Small airborne particles upon which water vapour condenses to form clouds. |
