People often think 究竟 (jiūjìng) is a simple word. Isn’t it only used in questions? Not quite.
In modern Chinese, 究竟 has three core uses: one as a noun, and two as an adverb.
In this post, we’ll break down all three, including their key structures, meanings, and common mistakes.
I. 究竟 as a noun: “the truth” or “the real story”
First, and probably the most overlooked use: 究竟 can function as a noun.
Here, it refers to the truth, the real circumstances, or what is really going on.
In modern Chinese, it normally appears as the object of a verb.
There are two common patterns.
Pattern 1: Verb + 个 + 究竟
This pattern is especially common in spoken Chinese and also appears in informal writing.
It means to get to the bottom of something—to find out what is really going on.
For example:
针对设备反复出现的异常响动，维修师傅没有敷衍了事，非要拆解开查个究竟。
Zhēnduì shèbèi fǎnfù chūxiàn de yìcháng xiǎngdòng, wéixiū shīfu méiyǒu fūyǎnliǎoshì, fēi yào chāijiě kāi chá ge jiūjìng.
“The technician refused to brush off the unusual noise coming from the equipment. He insisted on taking it apart to find out exactly what was going on.”
Here, 查个究竟 (chá ge jiūjìng) means to investigate and get to the bottom of something.
You can also say:
弄个究竟 (nòng ge jiūjìng) — to figure out what’s really going on
问个究竟 (wèn ge jiūjìng) — to get to the bottom of something by asking questions
探个究竟 (tàn ge jiūjìng) — to explore and find out what’s really going on
Pattern 2: Fixed expressions
In more formal or written Chinese, 究竟 also appears in fixed expressions such as:
一探究竟 (yí tàn jiūjìng) — to investigate and get to the bottom of something
For example:
听到门外一声巨响，爸爸立刻起身出去一探究竟。
Tīngdào ménwài yì shēng jùxiǎng, bàba lìkè qǐshēn chūqù yí tàn jiūjìng.
“When he heard a loud noise outside, Dad immediately went out to find out what had happened.”
You may also encounter the more formal expression:
探其究竟 (tàn qí jiūjìng) — to investigate the truth of the matter
So in this use, 究竟 refers to the truth or the real circumstances, rather than marking a question.
II. 究竟 as an interrogative adverb: pushing for the real answer
The second use is by far the most common.
As an interrogative adverb, 究竟 is used in questions to add a strong sense of insisting on finding the real answer.
It often carries the feeling of:
“What exactly…?”
“Who exactly…?”
“How exactly…?”
But there are two important rules.
Rule 1: Don’t use it with a simple question ending in 吗
究竟 works naturally with questions that ask you to identify, clarify, or choose an answer.
But it does not normally go with a simple 吗 question.
For example:
你究竟想做什么？
Nǐ jiūjìng xiǎng zuò shénme?
“What exactly do you want to do?”
But:
你究竟想去吗？
Nǐ jiūjìng xiǎng qù ma?
is not normally natural.
Why?
Because 吗 simply asks for a yes-or-no answer, while 究竟 adds the sense of pushing for the actual answer.
However, 究竟 can be used with positive-negative questions, such as 能不能 néng bù néng, 是不是 shì bù shì, 有没有 yǒu méi yǒu.
For example:
发布会下周就要举办，合作方究竟能不能给出确定的嘉宾名单？
Fābùhuì xià zhōu jiù yào jǔbàn, hézuòfāng jiūjìng néng bu néng gěichū quèdìng de jiābīn míngdān?
“The press conference is next week. Can the partner actually provide a confirmed guest list or not?”
So:
吗 → simple yes-or-no question
能不能 / 是不是 / 有没有 → positive-negative question, which can naturally take 究竟
Rule 2: When the question word is the subject, 究竟 comes before it
For example:
究竟谁泄露了这个消息？
Jiūjìng shéi xièlòu le zhège xiāoxi?
“Who exactly leaked this information?”
Here, 谁 is the subject, so 究竟 comes before it:
究竟谁……？
not:
谁究竟……？
The same principle applies to other question words, such as 什么 shénme and 哪一个 nǎ yīgè.
And with alternative questions, 究竟 can also push for a definite choice:
你究竟选线上还是线下参会？
Nǐ jiūjìng xuǎn xiànshàng háishì xiànxià cānhuì?
“Are you attending online or in person?”
So the key idea is simple:
When you’re asking someone to identify, clarify, or choose the real answer, 究竟 strengthens the question.
III. 究竟 as a declarative adverb: “after all”
Now for a less common use that many learners completely miss.
究竟 does not always indicate a question.
In some declarative sentences, it can emphasize a fundamental fact or characteristic, roughly corresponding to “after all” or “when you get right down to it.”
But there is an important point:
This use is less common and less natural in everyday speech than 毕竟 (bìjìng).
So don’t learn this as “究竟 and 毕竟 are interchangeable.”
Instead, you’ll mainly encounter this use in evaluative or more formal statements.
For example:
孩子究竟还小，不能要求他像成年人一样成熟。
Háizi jiūjìng hái xiǎo, bùnéng yāoqiú tā xiàng chéngniánrén yíyàng chéngshú.
“After all, he’s still a child. You can’t expect him to be as mature as an adult.”
Here, 究竟 is not asking anything.
It emphasizes the fundamental fact that he is still a child, which explains the judgment that follows.
Another example:
各类 AI 工具再高效也只是辅助，核心的商业判断究竟还是要靠人对行业的深度认知。
Gèlèi AI gōngjù zài gāoxiào yě zhǐshì fǔzhù, héxīn de shāngyè pànduàn jiūjìng háishi yào kào rén duì hángyè de shēndù rènzhī.
“No matter how efficient AI tools become, they’re still just aids. When you get right down to it, core business judgment still depends on deep industry expertise.”
Again, 究竟 is making a statement, not asking a question.
So remember:
In this use, 究竟 can emphasize a fundamental fact or conclusion, but in everyday Chinese, 毕竟 is usually the more natural choice.
CONCLUSION
So, to sum up, 究竟 has three important modern uses.
As a noun, it refers to the truth or the real circumstances, often appearing in expressions such as 查个究竟 or 一探究竟.
As an interrogative adverb, it strengthens a question and pushes for the real answer.
And as a declarative adverb, it can emphasize a fundamental fact or conclusion, similar to “after all”—though this use is less common than 毕竟.
The key is not to memorize one English translation for 究竟.
Pay attention to what the sentence is doing.
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