I was curious about いは in 或いは because ある is in its plain form however I can't find anything on it. I don't have any physical dictionary, either nor knowledge of if this is archaic Japanese


1 Answer 1


Surprisingly, this does seem to contain the 連体形 of ある, followed by an "adverbial particle" (副助詞) い which the etymology doesn't define, and the regular topic particle は.

The etymology explains that the original sense is ある人は ("a certain person"),ある場合は ("in a certain situation"), which is reflected in the first definition:

Demonstrates the fact that there exists a number of situations, by enumerating a sequence of related possibilities

For this first definition, the dictionary gives the example:

Either singing a song, or playing a flute

So together with the explanation ある場合は "In a certain situation", you can see that the original definition would have meant something like "In one case, singing a song; in another case, playing the flute".

This first definition was generalised to the more abstract notion of "X or Y".

  • I didn't check, thank you I made that question pretty late at night
    – Star Peep
    Apr 30, 2023 at 13:13
  • 1
    The Kotobank link confusingly went to the 回反 entry. I can only think that that must have been a copy-paste goof, so I have edited your answer post to link instead to the 或は entry, as I think you probably intended. 😄 May 1, 2023 at 18:12
  • Oops, thanks. But nice to learn a new abbreviation for "rotational symmetry" 😅
    – jogloran
    May 1, 2023 at 18:17

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