Ever since I learned that "if" and "when" can be used as translations for the -たら conditional form depending on the context, I have been looking for an explanation of its construction in terms of its etymology to have a proper understanding of how it works. The sources I have looked up say that it is formed from the "past tense" -た form + ら, but I have failed to find any information on this ら. Is it a classical Japanese auxiliary verb? Is the full form -たらば? Does it have anything to do with the 連体形 or attributive form of classical verb ending ~たり? Or is -たら the 仮定形 form of -た?

Please enlighten me on this topic so that I can stop translating this expression to English and start seeing it in terms of Japanese.

1 Answer 1


As regards the grammar of the modern Japanese, it is 仮定形1 of , auxiliary verb meaning past tense. At the same time, the standard etymology says た derives from たり2, so your guess is not totally off.


What is a little irregular about たら are:

  1. It can be used without ば, unlike most other 仮定形: The linked dictionary entry notes 仮定形「たら」は、多く「ば」を伴わないで「雨が降ったら中止だ」などと使われ、「遅いからもう帰ったら」のように文末に用いられて8の意を表す。

  2. For 仮定形, you may expect e-sound, i.e. たれ. But it retains classical 未然形: Wikipedia/已然形 notes 形容動詞とコピュラ「だ」、「た」だけは仮定条件の「ば」の前が未然形である文語の形式を残しているため「なら」、「たら3」になっている。

たら3 refers to the (classical) 未然形 of たり:


[補説] 中世以降は...「たる」を経て現代語の「た」に引き継がれる。

  • A concern about the Goo entry is that the part of speech for all of these, and indeed the usage examples, are none of them for mid-sentence conditional ~たら. The derivation given in the Goo entry is ultimately from といったら, whereas the derivation of the conditional ~たら is from ~て + あらば. This ~てあらば construction can be seen in the Man'yōshū, such as book 4, poem 581, or book 11, poem 2419. Commented Mar 22, 2023 at 16:59
  • 1
    Separately, you wrote that "た, auxiliary verb meaning passive." Surely you meant "past tense" instead? The Goo entry itself says 『過去の助動詞「た」』. Commented Mar 22, 2023 at 17:04
  • 1
    @EiríkrÚtlendi Thanks, I meant to link to た.
    – sundowner
    Commented Mar 22, 2023 at 23:23

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