act of God vs tragedy

act of God and tragedy both are nouns.

Word	Noun	Adjective	Verb	Adverb
act of God	Yes	No	No	No
tragedy	Yes	No	No	No

As nouns, tragedy is a hypernym of act of God; that is, tragedy is a word with a broader meaning than act of God:

act of God: a natural and unavoidable catastrophe that interrupts the expected course of events
tragedy: an event resulting in great loss and misfortune

Other hypernyms of act of God include calamity, cataclysm, catastrophe, disaster.

act of God (noun)	tragedy (noun)
a natural and unavoidable catastrophe that interrupts the expected course of events	drama in which the protagonist is overcome by some superior force or circumstance; excites terror or pity
	an event resulting in great loss and misfortune