12 letters · 24 points in Scrabble
noun an untroubled state; free from disturbances
noun a state of peace and quiet
noun a disposition free from stress or emotion
originFrom tranquil + -ity, from Middle English tranquillite, from Old French tranquillite, tranquilité, from Latin tranquillitas.
Etymology from Wiktionary, CC BY-SA 3.0