I was surprised by the sudden evening shower.

Lo and behold, he passed the exam.

I was taken aback by his sudden proposal.

I was really astonished by his sudden proposal.

Suddenly, it started to rain.

He suddenly stood up.

It started raining all of a sudden.

That disease is caused by a mutation.

He said, 'A sudden rainstorm separates horses,' teaching me the importance of facing sudden difficulties without fear.

Sudden Infant Death Syndrome refers to the sudden death of an infant for which the cause remains unknown.