Grammar Info
N4 Lesson 8: 1/18

When, From when, Just when, If

[な]Adjective + だった +
Noun + だった +
Register Standard
使用域 一般
The conjunction particle たら is used as a kind of 'halfway point' between 'if' and 'when' in Japanese. It expresses the completion of an (A) action, and then a (B) action that is considered to be the result of (A). It may be hypothetical, or it may be presenting a one-time result of something that happened in the past.
To use たら, it will replace た in the simple past form of verbs, い-Adjectives, な-Adjectives, and nouns.
  • 今度(こんど)遅(おく)れたら、許(ゆる)さない
    When/if you are next late, I will not let it slide.
  • 寒(さむ)かったら、エアコンつけ
    When/if you are cold, turn on the air conditioner.
  • 彼(かれ)事(こと)好(す)きだったら、彼(かれ)に言(い)った方(ほう)がいい
    When/if you like him, you should tell him.
  • 明日(あした)だったら、遊(あそ)べ
    When/if it is tomorrow, I can hang out.
Despite appearing to be the past form of the word that it is attached to, たら itself does not actually carry the nuance of 'past'. Other words in the sentence will need to be examined to see whether たら is truly highlighting something from the past, or simply the completion of something (which may or may not happen in the future).
  • 来週(らいしゅう)だったらいける
    If it is next week, I can go. (Highlighting a future event)
  • 先週(せんしゅう)だったら行(い)けのに
    If it was last week, I could have gone. (Highlighting a past event)
Fun Fact
Although たら is regularly used to mean 'if', it almost always has a nuance of 'when'. This is due to たら specifically highlighting the following situations:
Completion: 完了(かんりょう) - Completion of (A).
Materialization: 成立(せいりつ) - Coming to fruition of (A).
These meanings are opposed to other 'if' structures like , and なら, which focus far more strongly on the hypothetical 'if' meaning.
  • 買(か)い物(もの)に行(い)ったら、クッキー買(か)ってき
    When/if you go shopping, please get me some cookies.
  • あなたその本(ほん)読(よ)まないなら、私(わたし)読(よ)みます
    If you are not going to read that book, I will read it.
Slow Male
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When/if you study, the test will become easy.
[From when you study...]
Please let me know if/when the tea is weak.
[just when...]
If/when you want to go out to eat, let's go!
[行こう・from when...]
みんなの日本語 I
Page 158 [CH 25]
みんなの日本語 II
Page 66 [CH 35]
Marugoto Elementary 2 (A2) Rikai
Page 74 & 147
Genki II 1st Edition
Page 97
Genki II 2nd Edition
Page 123
[DBJG] A Dictionary of Basic Japanese Grammar
Page 452
Tae Kim's Japanese Grammar Guide
Page 137
[AIAIJ] An Integrated Approach to Intermediate Japanese
Page 17