かい (informal question)

• Reading: かい
• Romaji: kai
• Formation: Plain form + かい

Meaning

A sentence-final particle used in informal male speech to form yes-no questions. It adds a softer, friendlier tone compared to using か alone in casual contexts.

かい is a colloquial question particle primarily associated with male speakers, though some older women may use it as well. It attaches to the plain form of verbs, adjectives, and nouns (without だ for nouns and na-adjectives). Compared to plain か, which can sound blunt or even aggressive in casual speech, かい carries a warmer, more approachable nuance — it signals genuine curiosity or gentle concern. It is commonly used by fathers speaking to children, older men speaking to younger people, or between close male friends. かい is not used in formal situations or in writing. Learners should note that while かい softens a question, it still sounds distinctly masculine, so female speakers typically prefer の or plain intonation.

Examples

1. 元気かい。 How are you doing?
2. 今日は学校に行くかい。 Are you going to school today?
3. この映画は面白かったかい。 Was this movie interesting?

Usage Guide

Context: spoken, everyday

Tone: friendly

Do Say

• 朝ごはんは食べたかい。
• 新しい仕事はどうだい。
• 明日も来るかい。

Don't Say

• 先生、これは正しいですかい。(Mixing polite form with かい — かい is only for casual plain form) → 先生、これは正しいですか。
• 元気だかい。(Inserting だ before かい with na-adjectives — だ should be dropped) → 元気かい。

Origin & History

かい developed as a softened variant of か in the Edo period. The い suffix adds a gentle, familiar quality, similar to how ね softens statements. It became strongly associated with masculine casual speech.

Cultural Context

Generation: Adults and elderly

Social background: Universal