significant vs fundamental

significant is not a noun while fundamental is a noun.

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

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

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