かいkai“yes/no question ending”

かい is a sentence-ending particle that turns a casual sentence into a yes/no question. It is JLPT N4 grammar with a very particular voice: warm, a little old-fashioned, and usually spoken by a man, an older person or someone looking after a younger one. 元気かい？ — “You doing all right?”

You won’t need かい to ask your own questions — a plain rising 元気？ does that job. But you will hear it constantly in anime, manga, dramas and children’s books, and the JLPT expects you to recognise what it signals.

かい is the question particle か softened with い — the sound of a grandfather, a kind teacher or a father checking in.

What does かい mean?

かい adds a yes/no question to the end of a plain-form sentence, like か does. The difference is tone. Where a bare か at the end of a casual sentence can sound blunt or even rough, かい sounds gentle and friendly, with a slightly paternal feel:

• 行くか？ — Are you going? / Shall we go? (short, direct)
• 行くかい？ — Are you coming along? (friendly, inviting)

Think of the English difference between “You going?” and “Are you coming along, then?” Same question, different warmth.

かい only asks yes/no questions. For questions with a word like 何, どこ or どうして, the matching particle is だい: 何だい？ (“What is it?”), どうしたんだい？ (“What’s wrong?”). Learn the pair together.

How to form かい

かい goes straight onto the plain form. Nouns and な-adjectives attach without だ, just like the question particle か.

Two useful extensions:

• のかい / んかい — adds the explanatory の, asking for confirmation of something you’ve noticed: もう帰るのかい？ (“Oh, you’re leaving already?”). This is the かい version of のです.
• Question word + だい — 誰だい？, いつ来るんだい？ At N4 you only need to recognise these.

かい does not attach to です/ます. It belongs to plain speech, and mixing it with polite forms sounds like a period drama.

When is かい used?

• Adults to children. Teachers, parents and grandparents: 宿題は終わったかい？
• Older speakers in general. An elderly shop owner or neighbour: 学生さんかい？
• Men speaking kindly to friends or juniors. A senior colleague after work: もう一杯飲むかい？
• Fiction and narration. Characters written as gentle, wise or old-fashioned use かい heavily, and it appears in picture books and translated fairy tales.

It is casual and should never be used upward — not to a boss, a teacher or a customer. Women use it less than men, although older women do use it. Young people rarely use it among themselves; to them it sounds like a dad or a TV character.

かい example sentences

Example 7 is worth memorising. いいかい literally asks “Is it OK?”, but it works as “Listen” or “Now then” before advice or a warning. A teacher or coach says it right before the important part.

Nuance of かい

The い in かい does the softening. It makes the question sound caring rather than demanding. When an older man says 腹(はら)が減(へ)ったかい？ (“Hungry?”), he is not just collecting information — he is offering to feed you.

That same softness can sound slightly superior if used between equals. かい is the voice of someone who looks after people: a parent, a senior, a host. Coming from a young learner to a peer, it can sound as if you are talking down, or doing an impression. That is why most learners should recognise かい but ask their own casual questions with a rising plain form: 行く？ or 行くの？

💡 かい vs だい: かい is for yes/no questions (行くかい？). だい goes with question words (どこへ行くんだい？). Using かい with a question word — 何を食べるかい — is a common learner slip.

In writing, かい tells you a lot about a character. If a character in a reading passage says かい and だい, the writer is telling you they are older, male or in a caring role, and that the scene is relaxed.

かい vs か

Both end a yes/no question, and both attach to nouns without だ. The difference is register and tone.

For your own speech: use ますか politely, a rising plain form with friends (疲れた？), and leave かい to characters and older speakers until you know the social setting well. See か for the basics of the question particle.

Common mistakes with かい

Is かい on the JLPT?

In listening sections, a father or teacher character asking 〜かい？ is common. The answer choices test whether you understood it as a question, not a statement.

Practice questions for かい

Learning path for かい

Related grammar to review next

• か — the basic question particle that かい softens.
• かな — “I wonder,” another casual ending built on か, used when you aren’t directly asking anyone.
• かしら — the soft, traditionally feminine counterpart to かな.
• じゃないか — a casual ending that asks for agreement rather than a yes/no answer.
• ね — the everyday way to check in with someone warmly, without a formal question.

Learn かい with Hane

Hane’s listening drills put かい, か and rising plain questions side by side, so you can hear who is speaking and how. Practise N4 sentence endings in Hane.