fortuity(n = noun.event) accident, chance event, stroke - anything that happens suddenly or by chance without an apparent cause; "winning the lottery was a happy accident"; "the pregnancy was a stroke of bad luck"; "it was due to an accident or fortuity"
is a kind of happening, natural event, occurrence, occurrent
has particulars: hap, break, good luck, happy chance, coincidence, happenstance, lottery

   Accident; chance; casualty. D. Forbes (1750). [1913 Webster]

fortuity, n. (pl. -ies)
1 a chance occurrence.
2 accident or chance; fortuitousness.