fortuity vs occurrence

fortuity and occurrence both are nouns.

Word	Noun	Adjective	Verb	Adverb
fortuity	Yes	No	No	No
occurrence	Yes	No	No	No

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

fortuity: anything that happens suddenly or by chance without an apparent cause
occurrence: an event that happens

Other hypernyms of fortuity include happening, natural event, occurrent.

fortuity (noun)	occurrence (noun)
anything that happens suddenly or by chance without an apparent cause	an event that happens
	an instance of something occurring