fundamental vs significant

fundamental is a noun but significant is not a noun.

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

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

fundamental (adjective)	significant (adjective)
being or involving basic facts or principles	important in effect or meaning
serving as an essential component	too closely correlated to be attributed to chance and therefore indicating a systematic relation
far-reaching and thoroughgoing in effect especially on the nature of something	of considerable importance, size, or worth
	rich in significance or implication