1560s, "relating to music;" earlier (c.1500) armonical "tuneful, harmonious," from Latin harmonicus, from Greek harmonikos "harmonic, musical, skilled in music," from harmonia (see harmony). Meaning "relating to harmony" is from 1660s. The noun, short for harmionic tone, is recorded from 1777.
Noun Periodic motion whose frequency is a whole-number multiple of some fundamental frequency. The motion of objects or substances that vibrate or oscillate in a regular fashion, such as the strings of musical instruments, can be analyzed as a combination of a fundamental frequency and higher harmonics. ◇ Harmonics above the first harmonic (the fundamental frequency) in sound waves are called overtones. The first overtone is the second harmonic, the second overtone is the third harmonic, and so on.
Adjective Related to or having the properties of such periodic motion.