There are five main ways to form the conditional in Japanese and each has its own nuance or prescribed usage.

Ending	Conditional Form
〜たら	The General Case
〜ば	The Strong Conditional
なら	Basis
とすると	The Hypothetical
と	Natural Consequences

You can think of all but the last as being closely related—the nuance is in the degree to which you wish to stress the conditionality of the sentence.

In English we make a fairly clear distinction between “when” and “if”.

When I get home I’m going to make hot chocolate.

If I get home I’m going to make hot chocolate.

In Japanese the difference is not so well defined. For example, we could translate 〜たら as “when” or “if” depending on the context.

The conditional form using と is used to express a natural consequence of A—not an action that you will take. We will look at each of these in more detail.

The General Case (～ら)

The 〜たら form of the conditional is the most common and the safest for learners precisely because it is so universally applicable.

Verbs

To create the 〜たら conditional for all verbs we simply take standard past tense or negative and add ら.

Verb	Dictionary	+ve Conditional	-ve Conditional
to say	言いう	言いったら	言いわなかったら
to come back	戻もどる	戻もどったら	戻もどらなかったら
to see	見みる	見みたら	見みなかったら
to do	する	したら	しなかったら

仕事しごとが早はやく終おわったら、飲のみ会かいに参加さんかする。

If my work finishes early I will join for drinks.

出張しゅっちょうで京都きょうとに行いったら金閣寺きんかくじの写真しゃしんを撮とる。

If I go to Kyoto on a business trip I will take a photo of the kinkaku-ji.

今夜こんや、家いえに帰かえったらビールを飲のんでテレビを見みます。

Tonight when I get home I’ll drink a beer and then watch television.

So how do we know whether 〜たら means “when” or “if”? Well, you often know from the context of the sentence. Let’s look again the first example sentence above. If we translate the conditional as “when” it sounds strange: “When work finishes early I will join for drinks” (we don’t know for a fact that we will finish early). Equally, in the last sentence it’s reasonable to assume that you’re going to get home at some point so “when” is probably a more natural translation.

わからなかったら声こえをかけてください。

Give me a shout if you don’t understand.

金曜日きんようびだったらいいですね。

I wish it were Friday.

This way of creating the conditional is not limited to the standard past tense, we can also use it with the potential form, as well as the causative and passive forms which will be introduced later.

漢字かんじが読よめたら、日本にほんで働はたらけると思おもいますよ。

If you can read kanji then I think you can work in Japan.

Adjectives

We can change adjectives following exactly the same rules.

Adjective	Dictionary	+ve Conditional	-ve Conditional
interesting	面白おもしろい	面白おもしろかったら	面白おもしろくなかったら
easy	簡単かんたん	簡単かんたんだったら	簡単かんたんではなかったら

成績せいせきが良よかったら食事しょくじに行いきましょう。

If your grades are good let’s go for dinner.

部屋へやが寒さむかったら、眠ねむれない。

If the room is cold I won’t be able to sleep.

The Stronger Conditional (～ば)

Unlike 〜たら, 〜ば places more emphasis on the possibility that the first clause might not happen and, as such, is usually translatable as “if”.

Verbs

The 〜ば affirmative conditional ending is formed for all verbs by changing the “u” ending to an “e” ending syllable on the same row and adding ば.

する → すれ＋ば → すれば

For the negative conditional we replace the ending ない with なければ.

する → しない → しなければ

Verbs	Dictionary	+ve Conditional	-ve Conditional
to ask	聞きく	聞きけば	聞きなければ
to go home	帰かえる	帰かえれば	帰かえらなければ
to see	見みる	見みれば	見みなければ
to do	する	すれば	しなければ

お酒さけを飲のめば、眠ねむくなる。

If I drink alcohol I get sleepy.

また機会きかいがあれば一緒いっしょうに旅行りょこうしましょうね。

Let’s go on holiday together if we get another chance.

終電しゅうでんに間まに合あわなければ、泊とまってもいいですか。

If I miss the last train can I stay the night?

The 〜ば conditional is very often used to form a “What should I do?” type of question.

何なにを注文ちゅうもんすればいいですか？

What should I order?

彼女かのじょに会あったら何なにを言いえばいいですか？

When I meet her what should I say?

Like with 〜たら we can also change the potential form of the verb.

金曜日きんようびまでに回答かいとうが得えられれば大変たいへんありがたいです。

If I could get an answer by Friday it would be very much appreciated.

パスタでも作つくれなければティラミスは無理むりだね。

If you can’t even make pasta then Tiramisu is out of the question.

For the auxiliary verb, we need to use the literary form. We have three forms of the auxiliary verb:

Verbs	Dictionary	Polite	Literary
to be	だ	です	である

In terms of conjugation, you can think of the literary form of the verb as simply で and the verb ある, for which we already know the conjugation. Consequently, to form to the 〜ば conditional we follow the above rules to get であれば for the affirmative and でなければ for the negative.

到着日とうちゃくびが週末しゅうまつであれば迎むかえに行いけると思おもいます。

If you’re arriving at the weekend then I think I will be able to collect you.

彼かれは先生せんせいでなければ誰だれですか？

If he isn’t a teacher, then who is he?

Adjectives

For i-adjectives, we change the い into ければ.

Adjective	Dictionary	+ve Conditional	-ve Conditional
Light	軽かるい	軽かるければ	軽かるくなければ
Heavy	重おもい	重おもければ	重おもくなければ

この番組ばんぐみが面白おもしろくなければチャンネルを変かえてもいいですよ。

If this TV programme isn’t interesting you can change the channel.

“You can change the channel” is a more natural translation of the literal “even if you change the channel it’s good.

For na-adjectives, as you’ve probably worked out, we need the literary form of the auxiliary verb introduced above.

火曜日かようびが無理むりであれば他ほかの日ひを見みつけよう。

If Tuesday is impossible let’s find another day.

パスポートも必要ひつようであれば明日あしたに持もってきます。

If my passport is also required I will bring it tomorrow.

A Basis for a Statement (～なら)

なら places a much stronger emphasis on A being a condition to B. A close literal translation might be: “On the basis that the situation A exists, then B will occur/be true.” Unlike the previous conditionals, there is no need to alter verb forms or remember any particular rules—you simply add なら to dictionary form of the verb, adjective, or noun. Simple!

君きみならできるよ！

I know you have it in you!

明日あしたは飲のみ会かいがあるけど、来こられるなら嬉うれれしいです。

We’re having drinks tomorrow. I’d be happy if you could make it.

Note that the but conjunction is being used to introduce the topic of drinks to the conversation and would not get translated as “but” in English.

課長かちょうがオッケーと言いうなら今日きょうは早はやく帰かえりましょう。

If the department boss says it’s okay then let’s go home early today.

In Japanese companies more senior employees are often referred to by their title rather than their name.

弟おとうととけんかしないと約束やくそくするなら遊園地ゆうえんちに連つれていくよ。

If you promise not to fight with your little brother I’ll take you both to the amusement park.

You may see ば added to this form of the conditional. This does not change the meaning—it is merely another form of なら.

あまりにも恥はずかしいならば、発表はっぴょうしなくてもいいですよ。

If it’s really too embarrassing, you don’t have to make the presentation.

あまりにも looks like あまり but actually means something quite different. It comes before adjectives to mean “too much”, often with a negative connotation.

Natural Consequences (～と)

Where 〜たら, 〜ば and 〜なら preceded actions, と precedes a natural consequence (not typically an action that you will take).

と attaches itself to the dictionary form of the verb.

グラスが落おちると割われます。

If glass falls it will break.

テレビを消けすと静しずかになります。

If you turn off the TV it will become quiet.

However, it doesn’t have to be such a physically natural consequence; と can be used to imply that something always happens as if it were a natural consequence.

試験しけんが終おわると、習ならったことをすぐに忘わすれます。

Once exams have finished I immediately forget what I learnt.

The following, however, would be strange since going shopping with your friend is not a generally accepted truth upon finishing exams.

試験しけんが終おわると、友達ともだちと買かい物ものに行いきます。(✗)

Once exams have finished I will go shopping with my friend.

In this case the 〜たら form would be the better conditional form.

発車はっしゃサイン音おとが鳴なり終おわるとドアが閉しまります。

Doors close soon after the melody ends.

明日あしたは天気てんきが晴はれるといいですね。

It would nice if it’s sunny tomorrow.

〜といいですね is a common way of saying, “It would be nice if…” and is likely to appear on the JLPT N4/N5 examination.

For the auxiliary verb we add と to the standard form だ.

成績せいせきが６０点てん以上いじょうだと合格ごうかくになります。

60 points and above is a pass.

Adjectives

I-adjectives follow the same rules: just add the と particle after the dictionary form of the adjective. Na-adjectives take the auxiliary verb as above.

映画えいがが面白おもしろいといいですね。

Hopefully the film is good.

The Hypothetical

Whereas the other forms of the condition mainly differ based on the level of conditionality, とすると is used to present a purely hypothetical situation. In this sense, it is close to “were” and “would” in English. The structure uses と to append the verb “to do” to the prior verb. This “to do” verb is then changed into the conditional, giving us three possible structures.

1. 〜としたら
2. 〜とすれば
3. 〜とすると

You don’t tend to see とするなら so I’ve omitted it as an option from above.

Essentially, we use the same grammar as we learnt for the other conditionals but “double-up” on the verb. The nuance is identical for all three; although, at a push, you could argue that とすれば tends to be used more after nouns and adjectives.

留学りゅうがくするとしたら、イギリスに行いくだろう。

If I were to study abroad I suppose I would go to the U.K.

もしそれが事実じじつだとすればやめるでしょう。

Assuming that it’s true I guess I’ll resign.

時間じかんを遡さかのぼることができるとすればいつの時代じだいにする？

If you could go back in time to which era would you choose?

特とくに不自然ふしぜんなところはないけど、直なおすとしたらこの文章ぶんしょうを二ふふたつに分わけるでしょう。

There’s nothing particularly unnatural, but if I were to correct it I suppose I’d break the sentence into two.

全すべての条件じょうけんが同おなじだとすると、日本人にほんじんは日本製にほんせいの製品せいひんを好このむ。

All else being equal, the Japanese prefer Japanese-made products.

What about Moshi?

Many textbooks will introduce the conditional along with もし and consequently learners begin to associate this word with “if”. As we have seen, you do not need もし to form the conditional. So what does it do? Well, like how 〜たら, 〜ば and 〜なら express different levels of conditionality, もし merely emphasises the uncertainty of A happening in the first place or of B being a condition of A. It is placed before the conditional clause like so:

もし日本語にほんごが勉強べんきょうしたいと思おもっていたら教おしえますよ。

If you’re thinking you want to study Japanese then I’ll teach you.

もし京都きょうとに行いくなら、深夜しんやバスで行いくのが一番いちばん安やすいです。

If you’re going to go to Kyoto the night bus is the cheapest way.

もしよければまた会あいたいです。

If it’s okay with you, I’d like to see you again.

もしよかったら一緒いっしょうに行いきませんか。

If it’s okay with you, how about going together?

Note! もし cannot be used with と.