How to Use the Japanese Conditional たら | “If” and “When” Grammar

Introduction

Want to say “If…” or “When…” in Japanese?
Then it’s time to learn the たら-form:

👉 V / adj / noun (short past) + ら

This grammar lets you express conditional situations or what happens after a certain event.

Let’s look at how it works!

1. Meaning

💡 Pattern: V / adj / noun (short past) + ら, 〜 = If / When 〜

This pattern is used for:

• Conditions: “If it rains, I won’t go.”
• Sequences: “When I get home, I’ll call you.”
• Hypotheticals: “If I were a cat, I’d sleep all day.”

In an A たら B sentence, A has to occur before B. Or to put it another way, A has to occur in order for B to occur and B will always occur after A.

gokigen penguin

A たら B implies that B is true provided A is true / happens. Depending on context, this could be translated as ‘if A then B’, or ‘when A, then B’.

2. How to Form the たら Form

• Step1: Take the short past form of a verb , adjective or noun
• Step2: add ら

Affirmative

Negative

If you need a refresher on plain past tense conjugation, see these articles.

• Past Tense Plain Form (Short Form) – Verbs
• Past Tense Plain Form (Short Form) – Adjectives and Nouns

3. Example Sentences

Hypotheticals

• 私わたしが鳥とりだったら、空そらを飛とびたいです。
  → If I were a bird, I’d want to fly in the sky.
• 私わたしが猫ねこだったら、一日中いちにちじゅう 寝ねているでしょう。
  → I would sleep all day if I were a cat.

Conditions

• 暑あつかったら、ネクタイをしません。
  → If it’s hot, I won’t wear a tie.
• 高たかくなかったら、その靴くつを買かいます。
  → If it’s not expensive, I’ll buy those shoes.
• 雨あめが降ふらなかったら、公園こうえんに行いきます。
  → If it doesn’t rain, I’ll go to the park.

Sequences

• 授業じゅぎょうが終おわったら、電話でんわします。
  → I’ll call you when class ends.
• 宿題しゅくだいが終おわったら、遊あそびましょう。
  → Let’s play once we finish the homework.

4. Practice Time!

Talk about what you would do in the following situations, using たら.

🎯 Try 2 more with your own ideas!

5. Common Mistakes

Using dictionary form instead of short past

• 宿題が終わったら → ✅ OK
• 宿題が終わるら → ❌ NG

Using たら for reversed sequence

• 「スピーチがあったら、練習したほうがいい」→ ❌ NG
• ✅ Use なら instead, because B happens before A

Using past tense in B for a controllable action

In AたらB, B usually comes after A.

If B is in the past tense, it often describes something uncontrolled / unexpected that you noticed after A happened (a discovery), not a deliberate action.

✅ Natural (discovery / not controlled):

• 外そとに出でたら、雨あめが降ふっていました。= When I went outside, it was raining.
• 家いえに帰かえったら、だれもいませんでした。= When I got home, nobody was there.

❌ Unnatural (intentional action in past):

• 宿題しゅくだいが終おわったら、アニメを見みました。(This sounds odd because “watching anime” is a controllable action you chose to do.)
  • ✅Better ways to describe a past sequence you did intentionally: 宿題が終わった後、アニメを見ました。/ 宿題が終わってから、アニメを見ました。
  • ✅ For future / planned sequence, non-past B is fine: 宿題が終わったら、アニメを見ます。= When I finish my homework, I’ll watch anime.

6. Advanced Note: たら vs なら

• AたらB = A happens first, then B happens
• AならB = If A is true, then B applies

⛔ So don’t use たら if B happens before A!

Example: If you have a speech presentation next week, you should practice.

• Wrong: 来週らいしゅうスピーチがあったら、練習れんしゅうしたほうがいい。
• Correct: 来週スピーチがあるなら、練習したほうがいい。

gokigen penguin

In this example, the order of actions is: first you practice (B), and then you have a speech (A).
たら cannot be used for this sentence, because B (you practice) happens before A (have a speech).

7. Note: “もし” is optional

You can optionally add もし at the beginning of a たら sentence to emphasize “if”.

However, もし is not required—a sentence is still natural without it.

もし雨あめが降ふったら、キャンプに行いきません。 / 雨が降ったら、キャンプに行きません。
If it rains, I won’t go camping.

FAQ – Frequently Asked Questions

Conclusion

Now you can:

✅ Use 〜たら to express conditions and sequences
✅ Conjugate verbs and adjectives into たら-form
✅ Create natural “if/when” sentences in Japanese!

🎯 Challenge: What would you do if you won the lottery? Try answering in Japanese with 〜たら！