Main Entry:

ther·mo·sphere

Pronunciation:

\ˈthər-mə-ˌsfir\

Function:

noun

Etymology:

International Scientific Vocabulary

Date:

circa 1950

: the part of the earth's atmosphere that begins at about 50 miles (80 kilometers) above the earth's surface, extends to outer space, and is characterized by steadily increasing temperature with height

— ther·mo·spher·ic \ˌthər-mə-ˈsfir-ik, -ˈsfer-\ adjective