old growth vs woods

old growth and woods both are nouns.

Word	Noun	Adjective	Verb	Adverb
old growth	Yes	No	No	No
woods	Yes	No	No	No

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

old growth: forest or woodland having a mature or overly mature ecosystem more or less uninfluenced by human activity
woods: the trees and other plants in a large densely wooded area

Other hypernyms of old growth include forest, wood.

old growth (noun)	woods (noun)
forest or woodland having a mature or overly mature ecosystem more or less uninfluenced by human activity	the trees and other plants in a large densely wooded area