Most of the grammar sources that I have access to tell me that 場合 can be preceded by the 辞書形 or the た形, but none of them explain the semantic difference between the two uses.

This is clearly not a simple matter of time or completion, because the following sentence is given in みんなの日本語:


Here, the losing of the card has not yet happened or been completed. Various native speakers have assured me that the same sentence would be valid with なくす instead of なくした but exactly what the difference in meaning would be is not at all clear to me.

How does the use of the た形 and 辞書形 affect the meaning of 場合 sentences of this kind?

  • 4
    I can't answer your actual question but I just wanted to point at that, at the time you contact the card company, you have already lost the card, so the action of 'losing' is complete. Remember that the tense in Japanese is relative to the main clause, so なくした would make sense here. Jan 19, 2020 at 11:35
  • 3
    Various native speakers have assured me that the same sentence would be valid with なくす instead of なくした ← Really? I am left speechless...
    – user4032
    Jan 19, 2020 at 12:44

1 Answer 1


辞書形+場合 means "In the case someone will do the action". た形+場合 means "In the case someone has done the action".

I think "カードをなくす場合は、すぐカード会社に連絡してください。" is unnatural because no one will lose the card deliberately (will have no intention of losing the card). However, if you often lose the card, you can say like this "カードを(よく)なくす場合は、カードを財布の中に入れておきましょう。".

For example, in "切符を買う場合、みどりの窓口で買ってください。" and "切符を買った場合、車掌にその切符を見せてください。", 買う and 買った cannot be exchanged. 

  • I wonder if you could clarify a bit more because "In the case someone will do the action" isn't grammatical English, so I am not 100% sure I have understood correctly. Do you mean that the tenses work like 時 (which is well explained in the books, so if this is true, it would be great)? In other words: (1) た形 the second clause happens after the first, but in (2) 辞書形 the second clause happens before the first (you visit the window before you buy the ticket). Is that what you mean? Jan 20, 2020 at 10:17
  • I think so about (1). As for (2), I think "if you buy the ticket" is better. Jan 20, 2020 at 10:44
  • I wonder if you can edit your answer to include the 時 point. In a lesson today the teacher confirmed that the usage was identical. I could just answer my own question, but that would be unfair on you. Jan 22, 2020 at 13:11

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