The adverb 顿时 "suddenly"
The adverb 顿时 
indicates that an action was sudden and happened very quickly. It is most often used with verbs that express feelings, mental activity, emergence, and disappearance.
For example: to get excited, to become tense, to be filled with life, to sound.
indicates that an action was sudden and happened very quickly. It is most often used with verbs that express feelings, mental activity, emergence, and disappearance.
For example: to get excited, to become tense, to be filled with life, to sound. Pay attention
顿时 is used in written language.
Examples
气氛顿时紧张了起来
The atmosphere suddenly became tense
qìfēn dùnshí jǐnzhāng le qǐlái
The adverb 顿时 can be placed either at the beginning of a sentence or in the middle of a sentence. It is placed before a predicate expressed by either a verb or an adjective.
Examples
寂静的山村，顿时沸腾起来
A quiet mountain village suddenly filled with life
jìjìng de shāncūn, dùnshí fèiténg qǐlái
教室里顿时安静下来
The classroom fell silent for a moment
jiàoshì lǐ dùnshí ānjìng xiàlái
顿时，我的倦意消失了
Suddenly my weakness disappeared
dùnshí, wǒ de juàn yì xiāoshī le