fundamental vs fundamental frequency

fundamental and fundamental frequency both are nouns.

Word	Noun	Adjective	Verb	Adverb
fundamental	Yes	Yes	No	No
fundamental frequency	Yes	No	No	No

As nouns, fundamental and fundamental frequency are synonyms defined as:

fundamental and fundamental frequency: the lowest tone of a harmonic series

Other synonyms of fundamental include first harmonic.

fundamental (noun)	fundamental frequency (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

fundamental (adjective)	fundamental frequency (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