一言で言うと
- と: 100 certain. when X happens, Y happens, so more like 'when' than 'if'
- なら(ば): “if you are talking about…, then…“, used to give suggestions or advice, speculation, or requests .
- 〜たら: It implies a sequence: something happens after something else happens. 80% certain.
- 〜ば: denotes requirement: A is only (...) if B is (...). requires volition. Emphasises the future.
詳細
| Meaning context | と | なら(ば) | 〜たら | 〜ば | | ------------------------------------------------------------------------------- | -------------- | --------- | ------------------ | ------ | | certain results (when X happens, Y happens.) | ○ | ✕ | ○ (almost certain) | ○ | | natural consequences: After A happens, something is/happens because of it (...) | ○ (if certain) | ✕ | ○ | ○ | | advice or suggestion (if you have to choose one, take the one that (...)) | ✕ | ○ | ○ (〜たらいいですか) | △ | | requests | ✕ | ○ | ✕ | △ | | hypothetical, speculation (if it is the case that (...), it would be (...)) | ✕ | ○ | ○ | ○ |
| Can be used with... | と | なら | 〜たら | 〜ば | | -------------------- | ----- | --- | ------ | --- | | non-past | ○ | ○ | ✕ | ○ | | past tense | | | ○ 食べたら | ✕ | | Volitional | | | | ✕ | | 〜ますverb＋ | ○ | ✕ | | | | non-volitional verbs | yes | yes | yes | no | | Formal writing | ○ | ○ | ✕ | ○ | | common? | | | most | |
例文
それなら、簡単だ！ Oh, if that's the case, it must be easy! (e.g. receiving instructions on how to replace a battery. The listener extrapolates information that they heard, and conclude that it must be easy.)
それだと、簡単だ。 When that is the case, it is easy (e.g. describing different ways to solve differential equations. It is certain that if that is the case, finding the solution is easy.)
其れだったら、簡単だ。 If that has happened, it will be easy. (e.g. after you have installed the software, using it is easy.)
其れであれば、簡単だ。 If you get there, it will be easy. (e.g. telling you that, in the future, when you are older, you will understand.)
まあ、無理であれば、月曜日までに出してください。 まあ、無理なら、月曜日までに出してください。 Well, if it’s impossibility, turn it in by Monday.
Combined with どう to ask for an opinion 黒いスーツを着{{c1::たらどうですか}}？
〜ば with double actions
京都へ~~来れば~~、ぜひ連絡してください。 京都へ来たら、ぜひ連絡してください。 After you have arrived in Tokyo, please contact me!
If the subject for both sub-sentences is the same, you cannot use the ～ば form.
私は~~飲めば~~運転しないで。 私は飲んだら運転しないで。 If you drink, don't drive
Here, 飲めば would be wrong, because the subject of 飲む and 運転 is the same.
https://imabi.org/the-conditionals/