| A | B |
|---|
| Height of the land | Elevation |
| Elevation is measured from this | Sea level |
| Towards the river's mouth | Downstream |
| Towards the river's source | Upstream |
| Water, as in rain sleet or snow | Precipitation |
| Imaginary line that runs through the center of the earth | Axis |
| the earth makes a complete turn in one day | Rotation |
| The earth's trip around the sun | Revolution |
| The amount of moisture in the air | Humidity |
