particle N4 uncommon casual

〜かい — casual sentence-final question particle

〜かい・かい

Meaning

~? (casual yes/no question) — a softer, warmer spoken alternative to か for asking a yes/no question

Key sentence

もう宿題しゅくだいは終おわったかい。

Have you finished your homework?

Formation

Attaches to	Form	Example
Plain form (verb / i-adj / noun / na-adj)	[plain form] + かい	行いくかい / 元気げんきかい

When: Casual speech, with a friendly or fatherly tone; typically used by older or male speakers toward someone younger or close. Sounds gentler than blunt か.

Examples

今日きょうは来こないのかい。

You're not coming today?

それは本当ほんとうかい。

Is that really true?

When you can't use it

かい answers a yes/no question. For a question containing a question word (何なに, 誰だれ), the masculine だい is used instead — 何なにを食たべるんだい, not ×何なにを食たべるかい.

Easily confused with

〜だい Companion casual question particles: かい takes yes/no questions (来くるかい), だい takes question-word questions (どこへ行いくんだい). Same warm, somewhat dated register. か Plain か is the neutral question marker (and can sound brusque in casual speech); かい softens it into a friendly, familiar yes/no question.

See 〜かい in real sentences

Jengo shows 〜かい the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.

Study it in Jengo

Sources Compiled with reference to A Dictionary of Basic Japanese Grammar.

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