Chinese Grammar Bank

HOW TO USE 一下子

In this lesson, we’ll explore how to use 一下子 (yíxiàzi) to convey sudden actions, emotions, and changes.

We will differentiate between using 一下子 on its own and 一下子…就 to describe a quick action with an immediate result.

FOR SUDDEN ACTIONS & CHANGES

In this section, we’ll see how “一下子” can emphasise the suddenness or speed of an action or change.

This structure highlights the immediate and unexpected nature of the event without necessarily focusing on the result.

PATTERN

Subject + 一下子 + Clause

他一下子明白了这个问题。Tā yíxiàzi míngbái le zhège wèntí.He suddenly understood the problem.
门一下子关上了。Mén yíxiàzi guān shàng le.The door suddenly closed.
她一下子哭了起来。Tā yíxiàzi kū le qǐlái.She suddenly started crying.

KEY POINT || In these examples, “一下子” emphasises how quickly and suddenly the action or change occurred. The focus is on the rapidity of the event rather than its result.

TO EMPHASISE IMMEDIATE RESULTS

The structure 一下子…就 (yíxiàzi… jiù) not only conveys suddenness but also highlights an immediate result or outcome.

PATTERN

Subject + 一下子 + Clause 1, 就 + Clause 2

她一下子看懂了这本书，就开始写总结。Tā yíxiàzi kàn dǒng le zhè běn shū, jiù kāishǐ xiě zǒngjié.She understood the book at once and immediately started writing the summary.
他一下子摔倒了，就受伤了。Tā yíxiàzi shuāidǎo le, jiù shòushāng le.He suddenly fell and got injured.
孩子们一下子吃完了晚饭，就出去玩了。Háizimen yíxiàzi chī wán le wǎnfàn, jiù chūqù wán le.The kids finished dinner at once and immediately went out to play.

KEY NOTES || In these examples, “一下子” still conveys suddenness, but the addition of “就” emphasises the immediate outcome or result following the sudden action.

SIMILAR EXPRESSIONS

立刻 (lìkè)

立刻 means “Immediately,” “at once,” or “right away.”  In terms of the degree of formalness, “立刻” is more formal than “一下子”. 

​​Interchangeable use:

Both “一下子” and “立刻” convey the idea of something happening quickly, without delay.

They can often be used in contexts where a quick action or change is expected.

Examples:

他一下子就答应了Tā yīxià zǐ jiù dāyìngle.He agreed right away.
他立刻（就）答应了。Tā lìkè (jiù) dāyìngle.He agreed immediately.

立刻 is mostly interchangeable with “一下子” except “立刻” is more formal than “一下子“。

马上 (mǎshàng）

马上 is a synonym of “立刻“ and ”一下子“。

It also means  “Immediately,” “at once,” or “right away.”

In terms of the degree of formalness, “马上”  and ”一下子“ are less formal than “立刻“。 

Example:

他一下子就答应了。Tā yīxià zǐ jiù dāyìngle.He agreed right away.
他马上（就）答应了。Tā mǎshàng (jiù) dāyìngle.He agreed immediately.

KEY POINT || 马上 is usually used for human actions. For example, in this sentence, “门一下子关上了。” (The door suddenly closed.), we can’t use “马上” because the subject is “the door.”

突然 (tūrán)

Interchangeable use:

“一下子” and “突然” both suggest suddenness, but they differ in focus.

While “一下子” emphasises the speed or completeness of the action, “突然” focuses more on the unexpected nature of an event.

They can sometimes be used interchangeably in sentences where the surprise or abrupt nature of an event is the primary focus.

Example:

他一下子笑了。Tā yīxià zǐ xiàole.He suddenly laughed.
他突然笑了。Tā túrán xiàole.He suddenly laughed.

NOTE || Here, both can work, but “突然” subtly emphasises the surprise more, while “一下子” on the speed of the laughter.

Non-interchangeable use:

When “一下子” expresses the meaning of completing something fast, we can’t use “突然” interchangeably.

Example:

突然 cannot fit here as it doesn’t convey the sense of speed in completing the task.

他突然就完成了任务 conveys the meaning “He finished the task suddenly.”

COMPARISON TABLE

ExpressionMeaningFormalityTypical ContextKey Differences
一下子“All at once,” “suddenly”InformalEmotional shifts, quick actions, and task completion.Emphasizes speed, suddenness, or completeness.
立刻“Immediately”Neural/FormalUsed in formal or official contexts.Focuses on immediate action
马上“Right away”InformalOften used in casual speech, human actions.Less formal, typically involves quick actions by people.
突然“Suddenly,” “unexpectedly”NeutralSurprising events or external changes.Emphasizes unexpected nature rather than speed or completeness.

Let’s see more examples:

她一下子就明白了事情的真相。Tā yí xià zi jiù míng bái le shì qíng de zhēn xiàng.She understood the truth of the matter immediately.
她一下子哭了出来。Tā yí xià zi kū le chū lái.She burst into tears all of a sudden.
风一下子把窗户吹开了。Fēng yí xià zi bǎ chuāng hu chuī kāi le.The wind suddenly blew the window open.
他一下子就不见了踪影。Tā yí xià zi jiù bù jiàn le zōng yǐng.He suddenly disappeared.
我一下子忘了要说什么。Wǒ yí xià zi wàng le yào shuō shén me.I suddenly forgot what I was going to say.
他的脸一下子红了起来。Tā de liǎn yí xià zi hóng le qǐ lái.His face suddenly turned red.

TO SUMMARIZE

• 一下子 alone focuses on the suddenness or rapidity of an action or change.

• 一下子…就 emphasises not only the sudden action but also the immediate result that follows.

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FAQs

What does 一下子 mean in Chinese?

一下子 means “all of a sudden” or “in an instant,” used to describe something happening very quickly or unexpectedly.

How is 一下子 different from 一下?

一下 generally softens actions, meaning “a little” or “for a short time,” while 一下子 emphasizes suddenness or rapidity.

Can 一下子 be used with actions and states?

Yes, 一下子 can describe sudden actions, like 一下子跑了 (yíxiàzi pǎo le, “suddenly ran away”), or states, like 一下子明白了 (yíxiàzi míngbái le, “suddenly understood”).

Where does 一下子 appear in a sentence?

It typically appears before the verb or adjective to describe the sudden nature of the action or change, like 他一下子笑了 (tā yíxiàzi xiào le, “he suddenly laughed”).

Is 一下子 formal or informal?

一下子 is commonly used in spoken and informal written Chinese to convey spontaneity or abruptness.

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