means The lowest layer of Earth's atmosphere, where nearly all weather happens and where we breathe, extending from the ground up to about 7–20 kilometers depending on latitude.

from From the Greek 'tropos,' meaning 'turn' or 'change,' joined to 'sphaira,' a ball or globe — literally the 'sphere of change,' aptly named for the layer where air churns, mixes, and turns over endlessly. The naming belongs to the early 20th century, when scientists sounding the upper air discovered distinct atmospheric layers and needed words for each; 'troposphere' arrived alongside its calmer neighbor, the 'stratosphere.'