突然
tūrán
suddenly, all of a sudden
adverb
Example
天空突然下起了大雨。
Tiānkōng tūrán xià qǐle dà yǔ.
It suddenly started raining heavily.
A very common adverb used to describe unexpected or abrupt changes. Often appears at the beginning of sentences or before verbs to emphasize the sudden nature of an action.