～か～ないかのうちに vs. 次第

Question

According to my references, both of these are used in situations where one thing happens immediately after another. Here are some example sentences:

1. （火事を見た人の話）ドーンという音がして、１分たつかたたないかのうちに火が出てきました。
2. 彼は、５時のベルが鳴るか鳴らないかのうちに手を止め、工場を飛び出した。
3. （ニュース）　先ほど、関東地方で地震がありました。詳しい情報が入り次第、お伝えいたします。
4. すみません、もう少しお待ちください。分かり次第、お知らせしますので。

In all four cases, could you simply switch to the alternate construct with no change in meaning? Are there some examples where one or the other doesn't work, or perhaps a slightly different nuance between the two?

Answer 1

With 次第, the latter event that is to happen has to be done with volition. It cannot be a natural event. It has the nuance of 'having waited for the former event to end'. Your first example cannot be used with '次第' because fire is a natural event. The second one can be, because leaving the factory is a volitional event.

* ドーンという音がして、１分たち次第、火が出てきました。 [Ungrammatical]

彼は、５時のベルが鳴り次第手を止め、工場を飛び出した。

A か A ないかのうちに literary means 'within the time span where it is not even clear whether A had happened or not', or 'at around the moment that A is/was to happen'. It does not necessary mean that A has happened yet. Your examples 3 and 4 thus cannot be turned into this construction without the meaning being changed.

# 詳しい情報が入るか否かのうちに、お伝えいたします。

'We will let you know about it at around the moment we receive detailed information.' [It is strange. You cannot tell anything before knowing about it.]

# 分かるか否かのうちに、お知らせしますので。

By the way, as I gave in the examples above, A か A ないかのうちに is usually shortened to A か否かのうちに.　否 (ina) means negation. This construction is comparable to the English whether or not construction. In English, suppose you have the following example:

whether A or not A

You can avoid repeating the redundant A by putting the negation, the disjunct or and whether altogether, and omitting one of the A s:

= whether or not A

Similarly, in Japanese, instead of repeating A as in:

A か A ないか

you can put the disjunct か, negation and か 'whether' altogether. The only difference being that you have to use the negation 否 (ina) instead of the negation ない:

A かないか ==> A か 否 か

If you acknowledge the difference of word order between Japanese and English, you can see that this precisely corresponds to the English phrase word-by-word:

A か 否 か

A or not whether

Answer 2

次第 straightforwardly corresponds to "as soon as": it implies that some action should be taken as soon as some condition becomes true.

As you'll notice from your examples, the idiom かないかのうちに is often used to highlight that the action came earlier than expected. As in, some precondition was expected before the action, but the action happened before it was even clear that the precondition had completed.

1. （火事を見た人の話）ドーンという音がして、１分たつかたたないかのうちに火が出てきました。 The observer heard an explosion, and flames came bursting out no more than a minute later, maybe even less.
2. 彼は、５時のベルが鳴るか鳴らないかのうちに手を止め、工場を飛び出した。 The worker left his post at the factory as soon as the 5-o'clock bell rang; perhaps even a bit before.

Answer 3

Aか〜ないかB means what it does: you're in a situation where you don't even know whether A is or isn't, that already B. Definitely a favourite of amateurs of quantum mechanics. It's almost instantaneous, and often unrelated.

"No sooner had he passed the doorstep that it started to rain"
彼は家を出るか出ないかのうちに、雨が降り出した。

次第 has an implication cause, and is very formal compared to the other above. The most obvious example of implication is the famous:

It's up-to A.
A次第です。

It means that once A is done (if it's a thing) or has made a decision (if it's a person¹), then the rest will follow. Example situations: "What university will you attend? It depends on the results of the exams"; "Where shall we drink tonight? It's up to the boss." More complex uses should follow a similar implication pattern.

¹: I have a doubt. Maybe there is in this situation an ellipsis of the thing. "Aさん次第" would be "Aさんの判断次第". Hopefully, other replies or comments will clarify this :)