かい — Really? / Is that so? (masculine casual)
A casual question particle primarily used by male speakers. Softer than か alone; shows curiosity, mild surprise, or seeks casual confirmation.
Structure
[Plain form] + かい / [Noun / な-adj + な] + のかい
Examples
本当に行くのかい？
Hontou ni iku no kai?
Are you really going?
行く (plain) + のかい = mild surprise + seeking confirmation
もう帰るのかい、早いね。
Mou kaeru no kai, hayai ne.
Are you leaving already? That's early.
帰る + のかい = surprised comment
大丈夫かい？
Daijoubu kai?
Are you alright?
大丈夫 (na-adj) + かい = casual concerned question
• Key Concept: かい is primarily masculine and casual. • Question: Women typically use の？or かな. • Detail: Inappropriate in formal settings. • Detail: Often heard from fathers, older men, or mentor figures.
Commonly confused with
The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones かい is tested against.
vs か (plain question particle)
Plain か can sound blunt or interrogative; かい softens it into a warm, curious, distinctly masculine-casual question.
vs だい (question-word question ending)
だい pairs with question words (何だい, どこだい = 'what is it?', 'where?'); かい is for yes/no questions (行くのかい = 'are you going?').
vs かな (self-wondering)
かい is addressed TO a listener seeking their answer; かな is you musing to yourself, not really expecting a reply.
More sentence ending particles
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