Japanese has four ways to say "if," each with its own personality and restrictions. Using the wrong one won't be fatal, but using the right one will make your Japanese sound much more natural.
Overview of the Four Conditionals
| Conditional | Conjugation | Core personality |
|---|---|---|
| ば | Verb hypothetical form | Symmetrical; no past tense in result |
| たら | Verb た-form + ら | Most flexible; works with anything |
| と | Verb dictionary form + と | Inevitable result; no volition allowed |
| なら | Noun/Verb + なら | Hypothetical premise; loves giving advice |
ば: Symmetrical Conditions
The defining feature of ば is symmetrical conditions — if A then B, and if not A then not B:
| Example | Meaning |
|---|---|
| 田中さんが食べれば私も食べる。 | If Tanaka eats, I'll eat too. |
| 光に向かえば影は後ろになる。 | If you face the light, your shadow falls behind you. |
Restrictions of ば:
- The result clause cannot be past tense: 行けば見た ✗
- When the condition is an action verb, the result cannot express volition/commands/invitations: 行けば買おう ✗
- But when the condition is a stative or potential verb, it's fine: 行ければ博物館を見物しよう ○
ば appears extensively in proverbs: 光に向かえば影は後ろになる。 Face the light, and the shadow falls behind you.
たら: The Most Flexible
たら has almost no restrictions — it's the most versatile conditional:
| Example | Meaning |
|---|---|
| 駅に着いたら電話をしてください。 | Please call me when you arrive at the station. |
| 電気をつけたらここは明るくなった。 | When I turned on the light, the room became bright. |
| ペットを飼ったら、捨ててはいけない。 | Once you get a pet, you must not abandon it. |
The core of たら: B happens after A is completed — it emphasizes the completion of the condition.
Unique abilities of たら:
- The result can be past tense: 電気をつけたら明るくなった ○
- The result can be volitional/imperative: 着いたら電話してください ○
- It can express counterfactuals: もし電話をかけなかったら、あの飛行機に乗っていた ○
と: Inevitable Results
と means "whenever A happens, B inevitably follows" — natural laws, habits, inevitable cause and effect:
| Example | Meaning |
|---|---|
| 朝に起きると花が満開した庭に出る。 | When I wake up in the morning, I step out into the garden in full bloom. |
| 春になると桜が咲く。 | When spring comes, the cherry blossoms bloom. |
The biggest restriction of と: the result cannot contain volition/commands/invitations/requests:
| ✗ Incorrect | ○ Correct |
|---|---|
| 駅に着くと電話してください ✗ | 駅に着いたら電話してください ○ |
と is ideal for describing objective laws and cause-and-effect relationships — not for subjective intentions.
なら: Hypothetical Premise + Advice
The core of なら is "if that thing you mentioned is the case" — carrying a nuance of hypothesis and advice:
| Example | Meaning |
|---|---|
| 引っ越すなら、交通の便がいいところを探したほうがいい。 | If you're going to move, you'd better look for a place with good transportation. |
| バスなら、30分くらいかかる。 | If you take the bus, it'll take about 30 minutes. |
| 私が元気なら、行きます。 | If I'm feeling up to it, I'll go. |
Features of なら:
- Often used for giving advice
- The condition can be a noun (バスなら)
- The result cannot be past tense
Head-to-Head: Making the Right Choice
| Situation | Winner | Why |
|---|---|---|
| "Please call me when you arrive at the station" | たら | Result is a command/request |
| "Cherry blossoms bloom when spring comes" | と | Natural law |
| "If you go to Hokkaido, you can drink great milk" | ば | Symmetrical condition (go = can drink; don't go = can't) |
| "If you're moving, I'd suggest finding a place with good transit" | なら | Giving advice |
ては: Repeated/Negative Conditions
ては expresses "if you keep doing this (it's bad)":
甘いものを食べていては、太るよ。 If you keep eating sweets, you'll get fat.
Conjugation Quick Reference
| ば | たら | と | なら | |
|---|---|---|---|---|
| Verb | Hypothetical form | た-form + ら | Dictionary form + と | Dictionary form + なら |
| い-adjective | ければ | かったら | いと | — |
| な-adjective | であれば | だったら | だと | なら |
| Noun | であれば | だったら | だと | なら |
Summary
- ば: Symmetrical conditions; result cannot be past tense; the favorite of proverbs
- たら: Most flexible; works with everything; means "after A is done, B happens"
- と: Inevitable results; result cannot contain volition/commands
- なら: Hypothetical premise; great for giving advice
- When in doubt, use たら — it has the fewest restrictions
Self-Test
Q1. Why can't you say 「駅に着くと電話してください」?
Show answer
Because the result clause of と cannot contain volitional/imperative/request expressions. 「してください」 is a request, so と cannot be used here. It should be changed to たら: 「駅に着いたら電話してください。」
Q2. Is 「北海道へ行けば、おいしいミルクが飲める」appropriate with ば?
Show answer
Yes. This is a symmetrical condition — "if you go, you can drink great milk (if you don't go, you can't)." Additionally, the result is a potential expression (飲める), not a volitional/imperative one, so ば works perfectly here.
Q3. What should fill the blank in 「引っ越す＿＿、交通の便がいいところを探したほうがいい」?
Show answer
なら. This is giving advice — "if you're going to move, I'd suggest looking for a place with good transportation." なら is the best fit for the pattern "assuming a situation → giving advice."