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
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 った わなかった
to come back もど もどった もどらなかった
to see なかった
to do する した しなかった
仕事しごとはやわったら、かい参加さんかする。
If my work finishes early I will join for drinks.
出張しゅっちょう京都きょうとったら金閣寺きんかくじ写真しゃしんる。
If I go to Kyoto on a business trip I will take a photo of the kinkaku-ji.
今夜こんやいえかえったらビールをんでテレビをます。
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”.

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.

漢字かんじめたら、日本にほんはたらけるとおもいますよ。
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 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
成績せいせきかったら食事しょくじきましょう。
If your grades are good let’s go for dinner.
部屋へやさむかったら、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 しなければ
Verbs Dictionary +ve Conditional -ve Conditional
to ask なければ
to go home かえ かえ かえらなければ
to see なければ
to do する すれ しなければ
さけめば、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.
終電しゅうでんあわなければ、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.

なに注文ちゅうもんすればいいですか?
What should I order?
彼女かのじょったらなにえばいいですか?
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. To recap, we have three forms of the auxiliary verb:

Verbs Dictionary Polite Literary
to be 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週末しゅうまつであればむかえにけるとおもいます。
If you’re arriving at the weekend then I think I will be able to collect you.
かれ先生せんせいでなければだれですか?
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 かる かるければ かるくなければ
Heavy おも おもければ おもくなければ
この番組ばんぐみ面白おもしろくなければチャンネルをえてもいいですよ。
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.

火曜日かようび無理むりであればほかつけよう。
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!

きみならできるよ!
I know you have it in you!
明日あしたかいがあるけど、られるならうれれしいです。
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 so does not get translated as “but” in English.

課長かちょうがオッケーとうなら今日きょうはやかえりましょう。
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.

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.

グラスがちるれます。
If glass falls it will break.
テレビをしずかになります。
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.

試験しけんわるならったことをすぐにわすれます。
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.

試験しけんわる友達ともだちものきます。()
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おとわるドアがまります。
Doors close soon after the melody ends.
明日あした天気てんきれるいいですね。
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てん以上いじょう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.

映画えいが面白おもしろいいですね。
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?
とく不自然ふしぜんなところはないけど、なおとしたらこの文章ぶんしょう二ふふたつけるでしょう。
There’s nothing particularly unnatural, but if I were to correct it I suppose I’d break the sentence into two.
べての条件じょうけんおなじだとすると日本人にほんじん日本製にほんせい製品せいひんこのむ。
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勉強べんきょうしたいとおもっていたらおしえますよ。
If you’re thinking you want to study Japanese then I’ll teach you.
もし京都きょうとくなら、深夜しんやバスでくのが一番いちばんやすいです。
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 or もしよければ are very common phrases!

もしよかったら一緒いっしょうきませんか。
If it’s okay with you, how about going together?

もし cannot be used with と.

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