noun
vagary
VAY-guh-ree/vˈeɪɡɝi/
An unpredictable change in behavior or circumstances.
A sudden vagary of the weather interrupts the sunny picnic with rain.

Etymology
From “to wander,” vagary first meant a roaming journey or departure from usual conduct. Mental wandering supplied the bridge to an eccentric idea and, more broadly, an unpredictable departure from the expected.
In context
your back. Pasamonte, who was anything but meek being by this time thoroughly convinced that Don Quixote was not quite right in his head as he had committed such a vagary as to set them free),
More examples
- A vagary of the market wipes out their expected profit.
- We keep extra supplies to cope with the vagaries of shipping.
- She learns to handle the vagaries of her boss's moods.
Forms
vagary · vagaries
Similar words
- fluctuation
- Emphasizes variation in level or amount, not necessarily unpredictability.
- caprice
- Usually describes a sudden personal whim rather than changing circumstances.
- vicissitude
- Emphasizes changing fortunes in life, especially unwelcome changes.