All of a sudden means suddenly and unexpectedly. People use it for an event that sharply changes the situation, most often when telling a story about the past. It means the same as suddenly but sounds more conversational and lively, so in essays suddenly is the usual choice.
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all of a sudden + clause; clause + all of a sudden (= suddenly)
- I was reading quietly when all of a sudden the train stopped between two stations.
- All of a sudden, my manager asked me to present the report to the whole department.
- The morning was warm and sunny, but it got cold and windy all of a sudden.
What changed
First versionWe were watching a film when all of sudden the lights went out.
RevisionWe were watching a film when all of a sudden the lights went out.
The a in the middle of the phrase is easy to lose. But all of a sudden is a fixed expression, and the article is required. The version all of the sudden is often heard in American speech, but it is better avoided in writing.
All of a sudden only describes something that actually happens unexpectedly. It cannot mean “if something happens”: when you take a precaution, use in case: Take an umbrella in case it rains.
Your turn
We were halfway up the mountain when ___ thick fog came down and we lost the path.
Show the answer
all of a sudden — The fog came down unexpectedly, halfway up the mountain, so all of a sudden. All of sudden is missing the article, and the expression is not used without a.
Describe a time when your plans changed suddenly. Say what you were doing and what happened all of a sudden.
I was packing for a weekend trip when all of a sudden my flight was cancelled because of a storm.
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