Look at these two sentences:
A. この本を読んだら貸してあげるよ。
B. この本を読むなら貸してあげるよ。
Both are about lending a book. Translate them into English and they seem almost identical. But to a Japanese speaker, the mental images are completely different.
Sentence A: たら = I'll finish reading first, then lend it to you
この本を読んだら貸してあげるよ。
Timeline: I finish reading → Lend it to you
The speaker has the book and is reading it (or plans to). Once they finish (front clause completed), they'll lend it to you (back clause happens).
The core of たら: The front clause completes first, then the back clause happens.
Sentence B: なら = If you want to read it, I'll lend it to you now
この本を読むなら貸してあげるよ。
Timeline: Lend it to you → You go read it
The speaker heard you want to read this book, so they say "if you want to read it, here you go." The book goes to you first, then you read it.
The core of なら: Based on a hypothesis or premise, offer advice or take action. The back clause can happen before the front clause.
Timeline Comparison
| たら | なら | |
|---|---|---|
| Order | Front first → Back second | Back can precede front |
| Speaker's stance | Wait for condition, then act | Act based on assumption |
| Book example | I read it → lend to you | Lend to you → you read it |
Another pair:
| たら (sequential) | なら (hypothetical) |
|---|---|
| 日本に着いたら電話してください。 | 日本に行くなら、お土産を買ってきて。 |
| After you arrive in Japan, please call. | If you're going to Japan, bring me back a souvenir. |
With たら, you arrive first, then call — sequential order. With なら, you haven't gone yet, but I'm already asking you to buy something — I act on the assumption.
Another Key Trait of なら: It Loves Giving Advice
なら is perfect for "I heard you're going to do X → here's my suggestion":
| Example | Meaning |
|---|---|
| 引っ越すなら、駅の近くがいいよ。 | If you're going to move, near the station is good. |
| パソコンを買うなら、あの店が安い。 | If you're buying a computer, that store is cheap. |
| 日本語を勉強するなら、毎日聞くことが大事だ。 | If you're studying Japanese, listening daily is key. |
The common thread: the speaker is not setting a condition for the listener to fulfill. They're assuming the listener plans to do something, then offering their opinion.
This "giving advice" nuance is exclusive to なら. With たら, the sentence becomes a neutral "after you do X."
Another Key Trait of たら: It Accepts Everything
たら is the most flexible conditional — almost nothing is off-limits in the back clause:
| Back clause type | たら | なら |
|---|---|---|
| Command/request | ○ 着いたら電話してください | ○ 行くなら連絡してください |
| Past tense | ○ 開けたら猫がいた | ✗ |
| Volitional | ○ 終わったら帰りましょう | ○ |
たら's exclusive ability: the back clause can be in past tense. This is because たら can express "did something and then discovered...":
窓を開けたら雪が降っていた。 I opened the window and (discovered) it was snowing.
This "unexpected discovery" usage is unique to たら.
Exam Strategy: Look at the Back Clause
| Back clause feature | Choose | Reason |
|---|---|---|
| Advice (〜ほうがいい, 〜がいい) | なら | なら naturally gives advice |
| Past tense (〜た, 〜ていた) | たら | Only たら allows past tense |
| Pure sequential order | たら | たら emphasizes front-clause completion |
| Hypothesis + advice | なら | Advice based on assumption |
Summary
- たら: Front clause completes first → back clause happens next. The timeline is forward
- なら: Based on a hypothesis, offer action or advice. Back clause can precede front clause
- Same scenario (lending a book): たら = I read it then lend it; なら = you want to read it so I lend it
- Exam tip — check the back clause: advice → なら; past tense → たら
Self-Check
Q1. Fill in the blank: 「＿＿、駅の近くがいいですよ。」 — 引っ越したら or 引っ越すなら?
Show answer
引っ越すなら. The back clause is advice (駅の近くがいいですよ). なら is the best fit for "assuming you're going to do X → here's my suggestion."
Q2. Can 「窓を開けたら雪が降っていた」 be rewritten with なら?
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No. This sentence means "I opened the window and found it was snowing" — the back clause is past tense describing an unexpected discovery. なら cannot take past tense in the back clause, and this isn't a hypothesis — it actually happened. Only たら can express this "did something and then discovered" meaning.
Q3. Between 「この本を読んだら貸してあげる」 and 「この本を読むなら貸してあげる」, which one means "if you want to read it, I'll lend it to you"?
Show answer
「この本を読むなら貸してあげる」. なら means "if you want to read it" — based on the assumption that you want to read it, I'll lend it to you (the book goes to you first). The たら version means "after I finish reading it, I'll lend it to you" — I read it first, then the book reaches you.