means the layer of Earth's atmosphere above the troposphere, roughly 10 to 50 kilometers up, where temperature rises with altitude and the ozone layer sits — often used loosely to mean any dizzying height.

from Coined in the early 20th century by French meteorologist Léon Teisserenc de Bort, who stitched together Latin 'stratum' (a layer, from 'sternere,' to spread out — the same root that gives us 'street' and 'strata') with the Greek 'sphaira' (ball, globe). Literally 'the layered sphere,' named because he found this upper region surprisingly orderly and calm compared to the churning weather below.