たら — The versatile conditional (once / if / when)
The most versatile conditional, formed by adding ら to the past (た-)form. It means roughly 'once X happens, then Y,' enforcing a timeline where the first action completes before the second. It also handles 'if' and past discoveries ('when I did X, I found Y').
Structure
[Verb / い-adj た-form] + ら | [な-adj / Noun + だった] + ら
Examples
家に着いたら電話してください。
Ie ni tsuitara denwa shite kudasai.
Once you get home, please call me.
着いた (arrived) + ら (once that's complete)
冷蔵庫を開けたら、ケーキがなかった。
Reizouko wo aketara, keeki ga nakatta.
When I opened the fridge, the cake was gone.
discovery: doing A led me to find B (both clauses past)
安かったら、買いたい。
Yasukattara, kaitai.
If it's cheap, I want to buy it.
安かった (い-adj past) + ら = conditional 'if'
• The flexible one: unlike ば and と, たら freely allows commands, requests, and desires in the second clause (安かったら買いたい), so it's the safe default for 'if.' • Discovery rule: if both halves are past tense (開けたら、なかった), it means 'when X happened, I discovered Y,' not 'if.' • Time sequencing: A must finish before B — たら can't be used for two simultaneous actions.
Commonly confused with
The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones たら is tested against.
vs ば
ば is the general/hypothetical 'if' and dislikes commands or requests in the main clause. たら has no such restriction and adds a 'once A is done, then B' sequence.
vs と
と states an automatic/inevitable result ('whenever A, B') and can't take requests or volition after it. たら allows will, requests, and one-time events.
vs なら
なら responds to a topic/supposition someone raised ('if that's the case, if you're talking about X'), and B can precede A in time. たら requires A to happen before B.
More conditionals
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