- The parallel of latitude approximately 66°33′ north. It forms the boundary between the North Temperate and North Frigid zones.北极圈：北纬66°33′平行线。它形成北温带与北寒带的分界线
- magnesium carbonate
- magnesium hydroxide
- magnesium oxide
- magnesiums
- magnesium sulfate
- magnet
- magnet
- magnet-
- magnetic
- magnetic bottle
- magnetic bubble memory
- magnetic card
- magnetic compass
- magnetic core
- magnetic declination
- magnetic deviation
- magnetic dip
- magnetic disk
- magnetic equator
- magnetic field
- magnetic field strength
- magnetic flux
- magnetic flux density
- magnetic force
- magnetic head