good luck vs fortuity

good luck and fortuity both are nouns.

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

As nouns, fortuity is a hypernym of good luck; that is, fortuity is a word with a broader meaning than good luck:

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

Other hypernyms of good luck include accident, chance event, stroke.

good luck (noun)	fortuity (noun)
an unexpected piece of good luck	anything that happens suddenly or by chance without an apparent cause
a stroke of luck
an auspicious state resulting from favorable outcomes