vagary

/ˈveɪɡəri/
noun
  1. An unexpected and unpredictable change or action, often one that is difficult to explain.
    • The vagaries of the stock market make investing a challenge for beginners.
    • We had to adapt to the vagaries of the weather during our camping trip.
    • Her decision to quit her job and travel the world was just another vagary of her impulsive nature.