harmonic vs overtone

harmonic and overtone both are nouns.

Word	Noun	Adjective	Verb	Adverb
harmonic	Yes	Yes	No	No
overtone	Yes	No	No	No

As nouns, overtone is a hyponym of harmonic; that is, overtone is a word with a more specific, narrower meaning than harmonic:

harmonic: a tone that is a component of a complex sound
overtone: a harmonic with a frequency that is a multiple of the fundamental frequency

Other hyponyms of harmonic include first harmonic, fundamental, fundamental frequency, partial, partial tone.

harmonic (noun)	overtone (noun)
any of a series of musical tones whose frequencies are integral multiples of the frequency of a fundamental	a harmonic with a frequency that is a multiple of the fundamental frequency
a tone that is a component of a complex sound	(usually plural) an ulterior implicit meaning or quality

harmonic (adjective)	overtone (adjective)
of or relating to harmony as distinct from melody and rhythm
of or relating to the branch of acoustics that studies the composition of musical sounds
of or relating to harmonics
involving or characterized by harmony
relating to vibrations that occur as a result of vibrations in a nearby body