troposphere

 
Pronunciation: /ˈtrɒpə(ʊ)sfɪə, ˈtrəʊp-/

noun

  • the lowest region of the atmosphere, extending from the earth’s surface to a height of about 6-10 km (the lower boundary of the stratosphere).

Derivatives

tropospheric

Pronunciation: /-ˈsfɛrɪk/
adjective

Origin:

early 20th century: from Greek tropos 'turning' + sphere