happenstance (n.)

• accessory
• accident
• accidental
• addendum
• addition
• adjunct
• adventure
• appendage
• appurtenance
• auxiliary
• break
• casualness
• casualty
• chance
• circumstance
• collateral
• contingency
• contingent
• destiny
• episode
• event
• experience
• extra
• fact
• fate
• fluke
• fortuitousness
• fortuity
• fortune
• gamble
• hap
• happening
• hazard
• incident
• incidental
• indeterminacy
• indeterminateness
• inessential
• lot
• luck
• nonessential
• occasion
• occurrence
• opportunity
• other
• particular
• phenomenon
• probability
• reality
• risk
• secondary
• serendipity
• subsidiary
• supplement
• uncertainty