Meaning

noun compatibility in opinion and action

noun the structure of music with respect to the composition and progression of chords

noun a harmonious state of things in general and of their properties (as of colors and sounds); congruity of parts with one another and with the whole

originFrom Middle English armonye, from Old French harmonie, armonie, from Latin harmonia, from Ancient Greek ἁρμονία (harmonía, “joint, union, agreement, concord of sounds”), either from or cognate with ἁρμόζω (harmózō, “to fit together”), from Proto-Indo-European *h₂er- (“to join, fit, fix together”). First attested in 1602. Doublet of harmonia.

Etymology from Wiktionary, CC BY-SA 3.0