一体（いったい） means what on earth; what in the world; emphasis ~. It is a JLPT N3 grammar pattern used to add strong emphasis to questions, expressing surprise, frustration, or disbelief.
This grammar point often appears in neutral Japanese. If you want to add dramatic emphasis to questions, 一体（いったい） is a useful pattern to learn.
What does 一体（いったい） mean?
Use 一体（いったい） when you want to add strong emphasis to questions, expressing surprise, frustration, or disbelief.
Natural translations include:
- what on earth; what in the world; emphasis ~
- what on earth; what in the world; emphasis ~
- what on earth; what in the world
How to form 一体（いったい）
一体 + 何 / 誰 / どこ / どうして / どう / Question word
Examples of the pattern:
- いったい何
- いったい誰
- いったいどうして
When is 一体（いったい） used?
Use 一体（いったい） in situations like:
- rhetorical questions
- expressing frustration
- seeking clarification
Tone and register:
- neutral
- Common in rhetorical questions, test questions, and written narratives
一体（いったい） example sentences
- いったい何をしているんだ。 \u2014 What on earth are you doing.
- いったいどうして遅れたんだ。 \u2014 Why in the world are you late.
- いったい誰がそんなことを言ったんだ。 \u2014 Who on earth said such a thing.
- いったいどうなっているんだ。 \u2014 What in the world is going on.
- いったいいくらかかるんだろう。 \u2014 How much on earth will it cost.
Nuance of 一体（いったい）
The key nuance is adds force, emotion, or urgency to questions; never used in polite or gentle questions.
This matters because いったい is dramatic. It turns a normal question into a demand for explanation. It is common in arguments, mysteries, and sudden surprises..
For example:
- In rhetorical questions, it sounds natural and specific.
- Compared with たいてい, it carries a different weight and implication.
一体（いったい） vs たいてい
Both 一体（いったい） and たいてい can express what on earth, but they are different.
一体（いったい）:
- emphasis word for questions; adds dramatic force
たいてい:
- means usually; completely different meaning
Quick contrast examples:
- たいてい家にいる。 \u2014 I’m usually at home.
- いったい何をしているんだ。 \u2014 What on earth are you doing.
Common mistakes with 一体（いったい）
Watch out for these mistakes:
- Using it in polite questions (rude in formal contexts)
- Using it with statements instead of questions
- Confusing it with たいてい (usually)
Is 一体（いったい） on the JLPT?
Yes. 一体（いったい） is commonly taught as JLPT N3 grammar.
That means learners should be able to:
- recognize it in reading
- understand its nuance in context
- use it in simple original sentences
Practice questions for 一体（いったい）
Try making your own sentences with these prompts:
- Ask what on earth someone is doing.
- Express frustration about why something happened.
- Demand to know who said something.
Learn 一体（いったい） with Kanjiru
If you want to review 一体（いったい） together with kanji, vocabulary, and other JLPT N3 patterns, Kanjiru helps you practice Japanese in short, focused sessions.
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