- (in the classification of the earth's atmosphere by chemical properties) the region between the ionosphere and the exosphere, extending from about 250–650 miles (400–1050 km) above the surface of the earth.
- (in the classification of the earth's atmosphere by thermal properties) the region between the stratosphere and the thermosphere, extending from about 20–50 miles (32–80 km) above the surface of the earth.
- the atmospheric layer lying between the stratosphere and the thermosphere, characterized by a rapid decrease in temperature with height
- the solid part of the earth's mantle lying between the asthenosphere and the core
