ascent vs rapid growth

ascent and rapid growth both are nouns.

Word	Noun	Adjective	Verb	Adverb
ascent	Yes	No	No	No
rapid growth	Yes	No	No	No

As nouns, rapid growth is a hyponym of ascent; that is, rapid growth is a word with a more specific, narrower meaning than ascent:

ascent (noun)	rapid growth (noun)
the act of changing location in an upward direction	a rapid rise
a movement upward; rise above the ground
an upward slope or grade (as in a road)