Sudden (adjective)

1. Happening or coming quickly, without warning, or unexpectedly.
2. Done or acting quickly, without preparation or warning.
3. Occurring or acting with little or no apparent cause.

Origin:

Middle english sodein, from old english sēoden; akin to old high german sēdun sudden, latin subitus sudden, greek hekousios sudden.

Examples:

1. The sudden storm caught us by surprise.
2. He had a sudden urge to leave the country.
3. The sudden change in weather caused the flight to be delayed.
4. He made a sudden move and caught the ball.
5. The sudden death of the king caused a crisis in the kingdom.