か〜ないかのうちに
Pairs the affirmative and negative of the same verb to say that the second event happened just as the first was happening or had barely finished, when one could hardly tell whether it was complete: "no sooner... than...", "the moment...".
Verb (dictionary form)The basic form of a verb, as listed in a dictionary (non-past, affirmative).
行く・食べる・する・来る
Narrower than the plain form, which also covers 行かない・行った・行かなかった.
Verb (nai-form)The negative form of a verb, ending in ない.
行かない・食べない・しない・来（こ）ない
Verb (ta-form)The plain past form of a verb, ending in た／だ.
行った・食べた・した・来（き）た
Verb (nai-form)The negative form of a verb, ending in ない.
行かない・食べない・しない・来（こ）ない
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Setting the same verb side by side in affirmative and negative describes an instant when it is hard to tell whether the first action has even finished, and the second has already happened; it stresses an extremely short gap. The second clause usually describes something that happened, in the past tense, but it can also describe a recurring situation (店頭に並ぶか並ばないかのうちに売れていく). The first verb is usually in the dictionary form, though the た form is also possible. It is used in both written and spoken narration; in casual conversation 〜たとたん or 〜たらすぐ is also common.
Normally the same verb is repeated, once affirmative and once negative; with a compound verb the negative side can keep only the second half (言い終わるか終わらないかのうちに), but two verbs with different meanings cannot be used.
The second clause is normally not the speaker's intention, command or request; for an instruction, use another pattern: ベルが鳴ったらすぐ教室を出てください, 卵が完全に固まらないうちに取り出してください.
Note the の before うちに: 鳴るか鳴らないかのうちに; do not drop it.
- 1.たとたんN3With 「たとたん」 the first action, in the た form, is complete, and the second clause is usually a sudden or unexpected change (立ち上がったとたんにめまいがした); 「か〜ないかのうちに」 stresses that the second event happens almost simultaneously, just as the first occurs or is completed, with less sense of suddenness or surprise.
- 2.〜やいなやN1「やいなや」 follows the dictionary form and is literary, meaning the second event follows immediately; 「か〜ないかのうちに」 pairs the affirmative and negative of the same verb and stresses "almost simultaneously" even more.
All three mean "the moment...". With たとたん the first action is complete and the second is usually sudden or unexpected; やいなや is literary, with the second event following immediately; か〜ないかのうちに pairs affirmative and negative to stress that the two events almost overlap in time. None of the three normally takes the speaker's intention or request in the second clause.
