accident vs good luck

accident and good luck both are nouns.

Word	Noun	Adjective	Verb	Adverb
accident	Yes	No	No	No
good luck	Yes	No	No	No

As nouns, good luck is a hyponym of accident; that is, good luck is a word with a more specific, narrower meaning than accident:

accident: anything that happens suddenly or by chance without an apparent cause
good luck: an unexpected piece of good luck

Other hyponyms of accident include hap, break, happy chance, coincidence, happenstance, lottery.

accident (noun)	good luck (noun)
anything that happens suddenly or by chance without an apparent cause	an unexpected piece of good luck
an unfortunate mishap; especially one causing damage or injury	a stroke of luck
	an auspicious state resulting from favorable outcomes