12 letters · 22 points in Scrabble
noun the atmospheric layer between the mesosphere and the exosphere
originEtymology tree Proto-Indo-European *gʷʰer-der. Ancient Greek θερμός (thermós)der. English thermo- Ancient Greek σφαῖρᾰ (sphaîră)bor. Latin sphaera Late Latin sphērader. Old French spherebor. Middle English spere English sphere English -sphere English thermosphere From thermo- + -sphere.
Etymology from Wiktionary, CC BY-SA 3.0