burn down vs ruin

burn down is not a noun while ruin is a noun.

Word	Noun	Adjective	Verb	Adverb
burn down	No	No	Yes	No
ruin	Yes	No	Yes	No

As verbs, ruin is a hypernym of burn down; that is, ruin is a word with a broader meaning than burn down:

Other hypernyms of burn down include destroy.

burn down (noun)	ruin (noun)
	destruction achieved by causing something to be wrecked or ruined
	a ruined building
	an event that results in destruction
	failure that results in a loss of position or reputation
	the process of becoming dilapidated
	an irrecoverable state of devastation and destruction

burn down (verb)	ruin (verb)
burn completely; be consumed or destroyed by fire	fall into ruin
destroy by fire	destroy completely; damage irreparably
	reduce to ruins
	deprive of virginity
	reduce to bankruptcy
	destroy or cause to fail