firewood vs firebrand

firewood and firebrand both are nouns.

Word	Noun	Adjective	Verb	Adverb
firewood	Yes	No	No	No
firebrand	Yes	No	No	No

As nouns, firebrand is a hyponym of firewood; that is, firebrand is a word with a more specific, narrower meaning than firewood:

Other hyponyms of firewood include cordwood, backlog, brand, pine knot.

firewood (noun)	firebrand (noun)
wood used for fuel	someone who deliberately foments trouble
	a piece of wood that has been burned or is burning