population growth vs increment

population growth and increment both are nouns.

Word	Noun	Adjective	Verb	Adverb
population growth	Yes	No	No	No
increment	Yes	No	No	No

As nouns, increment is a hypernym of population growth; that is, increment is a word with a broader meaning than population growth:

population growth: increase in the number of people who inhabit a territory or state
increment: a process of becoming larger or longer or more numerous or more important

Other hypernyms of population growth include growth, increase.

population growth (noun)	increment (noun)
increase in the number of people who inhabit a territory or state	the amount by which something increases
	a process of becoming larger or longer or more numerous or more important