| Term | Definition |
| condensation | The change in matter where water changes from a gas to a liquid |
| evaporation | The change in matter when a liquid changes to a gas |
| transpiration | The process of when water moves through plants from their roots to their leaves. Water then leaves plants as vapor. |
| hygrometer | Tool tht measures humidity. |
| humidity | Water vapor in the air. |
| relative humidity | the amount of water vapor in the air measured in percentages. It compares the amount of water vapor in the air (in grams) to the amount of water vapor needed to saturate the volume of air. |
| saturated | when air contains as much water vapor as it can |
| dew point | the temperature at which air is saturated. |