brushwood vs vegetation

brushwood and vegetation both are nouns.

Word	Noun	Adjective	Verb	Adverb
brushwood	Yes	No	No	No
vegetation	Yes	No	No	No

As nouns, vegetation is a hypernym of brushwood; that is, vegetation is a word with a broader meaning than brushwood:

Other hypernyms of brushwood include botany, flora.

brushwood (noun)	vegetation (noun)
a dense growth of bushes	inactivity that is passive and monotonous, comparable to the inactivity of plant life
the wood from bushes or small branches	an abnormal growth or excrescence (especially a warty excrescence on the valves of the heart)
	all the plant life in a particular region or period
	the process of growth in plants