と・ば・たら・なら: Choosing a Conditional | Japanese Grammar

English has one conditional word — if — and it does everything. Japanese hands you four and makes you choose: と, ば, たら, and なら. The hard part of Japanese conditionals is not forming them — it is picking the right one, because they are not interchangeable stylistic variants. This page is a decision procedure. Instead of memorizing four "meanings," you run two fast diagnostic tests on the sentence and let them eliminate the wrong forms. For each form's full formation and secondary uses, follow its link; for a gentler side-by-side walkthrough see と / ば / たら / なら compared. Here, we only teach the choice.

The master decision table

Read this as a diagnostic grid, not a list of glosses. The two most powerful columns are the middle ones — they are what the two tests below check.

Form	Attaches to	Main clause may be a command / request / plan?	Main clause may occur before the condition?	Core feel
と	plain non-past (押す / 押さない)	Never	No	automatic, every-time result
ば	provisional (押せば / 安ければ)	Only if the condition is a state (adjective, negative, potential)	No	general / hypothetical "in principle"
たら	plain past + ら (押したら)	Yes — any main clause	No	a specific, one-time "once / when"
なら	plain form / noun (行くなら / 日本なら)	Yes	Yes — uniquely	"if it's the case that…" (given premise)

The whole procedure rests on the observation baked into those two columns: only と bans a volitional main clause, and only なら lets the main clause come first in time. Those two facts alone diagnose most sentences.

Test 1 — Look at the main clause first (the veto)

Before you think about "meaning," look at what follows the if. Is the main clause a command, request, invitation, suggestion, or a statement of your own will or plan (〜てください, 〜ましょう, 〜つもり, a volitional, "I'll…")? If so, two forms start dropping out:

と is out, always. You cannot order an inevitable result into being, so と never takes a command or a plan.
ば is out too — but only if the ば-condition is a controllable action. This is the nuance most textbooks skip. ば happily takes a command when its own condition is a state: an adjective, a negative, a potential.

このボタンを押すと、写真が撮れます。

kono botan o osu to, shashin ga toremasu

If you press this button, you can take a photo. (automatic result — と is fine)

写真を撮るなら、こっちのボタンを押してください。

shashin o toru nara, kotchi no botan o oshite kudasai

If you're going to take a photo, press this button. (request → と impossible, so not 撮ると)

使い方が分からなければ、遠慮なく聞いてください。

tsukaikata ga wakaranakereba, enryo naku kiite kudasai

If you don't understand how to use it, ask without hesitation. (ば + request is fine because the condition 分からない is a state)

That last one is the payoff of the nuance: 分からなければ、聞いてください is completely natural, whereas swapping in a controllable action — 東京に行けば、連絡してください — sounds off. The test is not "is there a command?" but "is there a command and a controllable ば-action?"

💡

Fastest reflex in the whole system: let the main clause veto first. A command, request, invitation, or plan crosses out と on the spot — and crosses out ば too unless the condition is a bare state. That single move eliminates the most common English-speaker error before you weigh anything else.

Test 2 — Can the main clause happen before the condition?

Here is the second diagnostic, and it is a clean one-way street. Only なら lets the main-clause event occur earlier in time than the condition. With と, ば, and たら the main clause always follows the condition; if your sentence needs the reverse order, the form is forced.

出かけるなら、傘を持って行ったほうがいいよ。

dekakeru nara, kasa o motte itta hō ga ii yo

If you're going out, you should take an umbrella. (you grab the umbrella BEFORE going out → only なら)

車を買うなら、決算セールの今がお得だよ。

kuruma o kau nara, kessan sēru no ima ga o-toku da yo

If you're going to buy a car, now — during the end-of-fiscal-year sale — is a bargain. (act now, buy later → なら)

Test the umbrella sentence against たら: 出かけたら、傘を持って行って means "after you've gone out, take an umbrella," which is nonsense — you can't fetch an umbrella once you've already left. The time-reversal is a fingerprint of なら: whenever the advice or action comes ahead of the conditional event, なら is the only form that fits.

💡

The reversal test is decisive. If the main clause describes something you'd do before the "if" event happens (buy a guidebook before the trip, grab an umbrella before leaving), the answer is なら — no other conditional can run time backwards.

When no veto fires — sort by where the condition comes from

If Test 1 finds no command and Test 2 finds no reversal, the main clause is a plain statement or result, and all four are still on the table. Now pick by the nature of the condition:

Automatic, every-time law (machines, nature, directions, math) → と. There is a sense of "each and every time."

春になると、この川沿いは桜でいっぱいになる。

haru ni naru to, kono kawazoi wa sakura de ippai ni naru

When spring comes, this riverside fills up with cherry blossoms.

General or evaluative hypothesis, often with an adjective, "it would be good/cheaper/better if" → ば.

天気さえよければ、あの山からの景色は最高なんだ。

tenki sae yokereba, ano yama kara no keshiki wa saikō nan da

As long as the weather's good, the view from that mountain is unbeatable.

A specific, one-time event on a concrete occasion → たら (also the safe default whenever you're unsure).

仕事が片付いたら、久しぶりに温泉でも行かない？

shigoto ga katazuitara, hisashiburi ni onsen demo ikanai?

Once work is wrapped up, want to go to a hot spring for the first time in ages?

Reacting to a premise just raised — something the other person said or a situation now on the table → なら.

そんなに頭が痛いなら、今日は早く帰ったら？

sonna ni atama ga itai nara, kyō wa hayaku kaettara?

If your head hurts that much, why not head home early today? (responding to what they just told you)

The procedure, start to finish

Run any sentence through these three steps and the form falls out:

Is the main clause a command, request, invitation, plan, or your own will?
- Yes → cross out と. Cross out ば too, unless the condition is a state. Continue to step 2.
- No → skip to step 3.
Does the main clause happen before the condition in time?
- Yes → なら.
- No → たら by default — or なら if you're reacting to a premise the other person just put on the table.
(Plain result.) Automatic every-time law → と. General/evaluative hypothesis → ば. One specific occasion → たら. Picking up a raised premise → なら.

Worked example. Someone tells you 頭が痛い ("my head hurts") and you want to suggest going home. Step 1: the main clause is a suggestion (帰ったら？) → と out, and ば out because the reply reacts to a person's controllable plan. Step 2: no time reversal, but you're clearly responding to what they just said → なら. Result: 頭が痛いなら、早く帰ったら？ The procedure delivered the form without any guesswork.

Common mistakes

❌ 窓を開けると、写真を撮ってください。

mado o akeru to, shashin o totte kudasai

Incorrect — と can never be followed by a request.

✅ 窓を開けたら、写真を撮ってください。

mado o aketara, shashin o totte kudasai

Once you open the window, please take a photo. (request → たら)

❌ 出かけたら、傘を持って行って。

dekaketara, kasa o motte itte

Wrong time order — たら puts fetching the umbrella AFTER you've already left.

✅ 出かけるなら、傘を持って行って。

dekakeru nara, kasa o motte itte

If you're going out, take an umbrella (with you before you go). (reversal → なら)

❌ 大学を卒業すれば、就職するつもりです。

daigaku o sotsugyō sureba, shūshoku suru tsumori desu

Off — ば resists a same-subject controllable action (卒業する) plus a plan (つもり).

✅ 大学を卒業したら、就職するつもりです。

daigaku o sotsugyō shitara, shūshoku suru tsumori desu

When I graduate, I plan to get a job. (one-time event + plan → たら)

❌ 東京に行くと、連絡します。

Tōkyō ni iku to, renraku shimasu

Incorrect — a one-time trip plus 'I'll be in touch' (your own will) can't take と.

✅ 東京に行ったら、連絡します。

Tōkyō ni ittara, renraku shimasu

When I go to Tokyo, I'll be in touch. (specific occasion + will → たら)

Every one of these is caught by Test 1 or Test 2. The と errors are volitional main clauses that と forbids; the たら/なら error is a time reversal only なら can handle; the ば error is a controllable same-subject action where ば's command tolerance runs out.

Key takeaways

Two tests, then a sort. Check the main clause for a veto (Test 1), check for time reversal (Test 2), then sort the survivors by the nature of the condition.
Only と bars a volitional main clause — commands, requests, plans, and "I'll…" all rule と out immediately.
Only なら can run time backwards — if the main clause happens before the condition, なら is forced.
ば tolerates a command only when its condition is a state (分からなければ聞いてください ✓; 東京に行けば連絡してください ✗).
たら is the safe default for a specific one-time event whenever the two tests don't force another form.

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