Pronunciation: [ˈɔːl ɒv sˈʌdən] (IPA) 
The correct spelling of the phrase is "all of a sudden", not "all of sudden". The "a" is necessary to indicate that the sudden event happened in a moment. The correct pronunciation is [ɔːl əv ə ˈsʌdn], with the stress on the first syllable of "sudden". It is a common phrase used to describe a sudden or unexpected occurrence, and it is important to spell and pronounce it correctly to avoid confusion or misunderstanding.
The phrase "all of a sudden" is an idiomatic expression that is used to describe an unexpected or abrupt occurrence or change in a situation. It is often used to convey a feeling of surprise or astonishment. This term is also commonly used interchangeably with similar expressions such as "out of the blue" or "without warning."
The phrase "all of a sudden" refers to a dramatic shift or event that happens unexpectedly, catching someone off guard or causing immediate attention or reaction. It implies that there was no prior indicator or anticipation of the event or situation that unfolds. This phrase can be used to describe various scenarios, including sudden weather changes, unexpected outcomes in a particular situation, or the abrupt appearance or disappearance of something or someone.
For example, one might say, "I was walking down the street when, all of a sudden, it started pouring rain!" This suggests that the rain began without warning and was a surprising development. Another example could be, "She was talking to me calmly, but then, all of a sudden, she screamed and ran away." This implies that the change in behavior was sudden and unexpected.
In summary, "all of a sudden" is an idiomatic expression that signifies an unexpected or abrupt occurrence, typically lacking any preceding indication or anticipation.
