Structure:

突然/ 忽然 + Verb

Meaning:

突然 and 忽然 both can put in the sentence as adverbs or adjectives, just make sure to put them before the verb or the adjective!

Examples:

    睡觉 的 时候，我 的 电话突然 响了。

    Shuì jiào de shí hou ， wǒ de diàn huà tū rán xiǎnɡ le .

     While I was sleeping, my phone suddenly started to ring.

 

        Before an Adjective
Structure:

突然/ 忽然 + Adjective

Examples:

    天 突然 暗 了。(Tiān tū rán àn le 。 )
天 忽然 暗 了。(Tiān hū rán àn le 。)
The sky suddenly got dark.

At the Beginning of a Sentence

You can place 突然 and 忽然 at the beginning of a sentence, just make sure to add a comma after it!

Structure:

突然/ 忽然, ….

Examples:

    突然，他 进来 了。(Tū rán ， tā jìn lái le 。 )
忽然，他 进来 了。(Hū rán ， tā jìn lái le 。 )
Suddenly, he entered.