Pronunciation: /ɔːl əv ə ˈsʌdən/
adverb modifies a verb, adjective, or another adverb to indicate a sudden or unexpected event
A1 All of a sudden, the cat jumped off the table.
A2 I was walking in the park when all of a sudden it started raining.
B1 All of a sudden, the power went out in the entire neighborhood.
B2 She was enjoying her vacation when all of a sudden she received a call from work.
C1 The negotiations were going smoothly until all of a sudden one party walked out.
C2 All of a sudden, the stock market crashed, causing panic among investors.
preposition shows the relationship between 'all' and 'sudden', indicating that the sudden event involves everything mentioned
A1 All of a sudden, the lights went out.
A2 I was walking in the park when all of a sudden it started raining.
B1 All of a sudden, she remembered where she left her keys.
B2 The car broke down all of a sudden, leaving us stranded in the middle of nowhere.
C1 The company's profits dropped all of a sudden, causing concern among the shareholders.
C2 All of a sudden, he realized the true extent of his feelings for her.
formal All of a sudden, the stock market crashed, causing panic among investors.
informal I was just sitting there minding my own business when all of a sudden, she showed up out of nowhere.
slang I was chilling at the park when all of a sudden, my ex walked by with their new boo.
figurative The peaceful atmosphere was shattered when, all of a sudden, a loud explosion echoed through the valley.
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