| A | B |
|---|
| Air mass | a large region of the atmosphere where the air has similar properties throughout |
| Front | a boundary between air masses with different temperatures |
| cold front | a boundary where cold air moves in under a mass of warm air |
| Warm front | a boundary where warm air moves in over a mass of cold air |
| occluded front | a front formed where a cold front moves in under a warm front |
| stationary front | an unmoving front where cold air mass and a warm air mass meet |
