first harmonic vs fundamental

first harmonic and fundamental both are nouns.

Word	Noun	Adjective	Verb	Adverb
first harmonic	Yes	No	No	No
fundamental	Yes	Yes	No	No

As nouns, first harmonic and fundamental are synonyms defined as:

Other synonyms of first harmonic include fundamental frequency.

first harmonic (noun)	fundamental (noun)
the lowest tone of a harmonic series	the lowest tone of a harmonic series
	any factor that could be considered important to the understanding of a particular business

first harmonic (adjective)	fundamental (adjective)
	being or involving basic facts or principles
	serving as an essential component
	far-reaching and thoroughgoing in effect especially on the nature of something