Suddenly means all at once, without any warning. He suddenly stopped. Suddenly the lights went out. It is one of the most useful adverbs in storytelling and one of the most overused.
It moves freely in a sentence — at the front for drama, before the verb for neutrality — and both are correct. Note all of a sudden, which means exactly the same and is more informal, and the adjective sudden, which is used mostly before nouns: a sudden noise, a sudden change. Writers are often advised to cut suddenly on the grounds that a sudden event reads as sudden without being labelled, and the advice is usually right.
1adverbsuddenlyAll at once, with no warning.
“The rain stopped as suddenly as it had started.”
synonyms: abruptly, all at once, unexpectedly
suddenly is a manner of happening.
Also accepted in games: abruptly
Middle English
sodenly
English, today
suddenly
Middle English sodenly, sodeynly, sodeinliche, sodaynlyche; equivalent to sudden + -ly.
Etymology from Wiktionary, CC BY-SA