Conditionals (条件文)

Many situations in our lives are limited to specific cases or conditions. You will be introduced to frequently used conditional clauses that express such situations and show exactly when and how you can use each conditional clause.

. . . たら tara (whenever, when, if )

You can create the tara form of verbs and adjectives just by adding ら ra at the end of the ta form (plain past affirmative form). It is very similar to the tari form. For example, the ta form of 行く iku (to go) is 行った itta, and its tara form is 行ったら ittara.

The clause that ends in たら tara (called the tara clause) is interpreted differently depending on the tense of the main clause, but it always requires that the situation in the tara clause precede the situation in the main clause. When the main clause is in the non-past tense, the tara clause expresses a generic condition or a non-generic condition.

Generic condition (一般的な状態)

Some events or situations almost always result in a specific outcome due to inherent facts in nature, mathematics, society, family, and so on. When a tara clause expresses such a generic condition, the main clause expresses what is predicted to happen whenever the condition is met. Accordingly, the main clause does not express the speaker’s controllable act, requests, suggestions, etc. The following are some examples of sentences that express generic conditions:

春になったら、雪はとけます。Haru ni nattara, yuki wa tokemasu. The snow will melt when spring comes.
7時になったら、母が帰ります。Shichi-ji ni nattara, haha ga kaerimasu. When it’s 7 o’clock, my mother will come home.
風をひいたら、鼻水が出ます。 Kaze o hiitara, hanamizu ga demasu. If you catch a cold, you’ll have a runny nose.

Non-generic condition (非一般的な状態)

An event or a situation can serve as the condition for someone to act in a certain way after it is met. In this case, the main clause can express the speaker’s controllable act, suggestions, requests, etc. Such a non-generic condition can be temporal or hypothetical, depending on the likelihood that the condition will be met. For example:

高橋さんが来たら、私は帰ります。Takashi-san ga kitara, watashi wa kaerimasu.

When Mr. Takahashi comes, I will go home. (temporal condition)

I’ll go home if Mr. Takahashi comes. (hypothetical condition)

The adverb もし moshi (if ) is often used for hypothetical conditions. Additional examples of non-generic conditions are:

五時になったら、電話しますね。Go-ji ni nattara, denwa shimasu ne. When it’s 5 o’clock, I’ll call you, okay? (or I’ll call you when it’s 5, alright?) (temporal condition)
もし病気になったら、休みます。Moshi byōki ni nattara, yasumimasu. If I become sick, I will take a day off. (or If I get sick, I'll rest.) (hypothetical condition)

When the main clause is in the past tense, a sentence with a tara clause expresses what happened after doing something. For example:

ドアを開けたら、犬が外に出ました。 Doa o aketara, inu ga soto ni demashita. When I opened the door, the dog went outside.

Do not use a tara clause if two actions were intentionally performed by the same person when the main clause is in the past tense. In that case, use the te form to connect the actions. For example:

ドアを開けて、猫を外に出しました。 Doa o akete, neko o soto ni dashimashita. I opened the door and let the cat outside.

. . . ば ba (whenever, when, if )

You create the ba form of verbs and adjectives as follows:

Ru verbs: Replace ru at the end of the dictionary form with reba (e.g., 食べる taberu (to eat), 食べれば tabereba).
U verbs: Replace ru at the end of the potential form with ba (e.g., 書く kaku (to write), 書けるkakeru (to be able to write), 書けばkakeba).
Irregular verbs: する suru, すれば sureba; くる kuru, くれば kureba.
I adjectives: Add kereba after the stem (e.g., 高い takai (expensive), 高ければ takakereba). The ba form of いい ii is よければ yokereba.
Na adjectives: Add であれば de areba after the stem (e.g., 静かな shizuka na, 静かであれば shizuka de areba).
Copular verb: Replace だ da or です desu with であれば de areba (e.g., 学生だ gakusei da, 学生であれば gakusei de areba).
Negative forms of verbs and adjectives: Create the nai form and treat it as if it is an i adjective, regardless of whether it is a verb or an adjective (e.g., 食べない tabenai (not to eat), 食べなければ tabenakereba; 高くない takaku nai (not expensive), 高くなければ takaku nakereba; 静かじゃない shizuka ja nai (not quiet), 静かじゃなければ shizuka ja nakereba; 学生じゃない gakusei ja nai (not to be a student), 学生じゃなければ gakusei ja nakereba).

The clauses that end with ば ba (called ba clauses) express all kinds of conditionals that the tara clauses can express, except that the main clause cannot express a command, request, suggestion, etc., if the predicate in the ba clause denotes an action or event. See the contrast among the following sentences:

山田さんが来たら、一緒に映画を見ませんか。Yamada-san ga kitara, isshoni eiga o mimasen ka. If Yamada comes, shall we watch a movie together?
山田さんが来れば、一緒にテニスをしませんか。(ungrammatical) Yamada-san ga kureba, isshoni tenisu o shimasen ka. (Intended: If Yamada comes, shall we play tennis together?)

Unlike tara clauses, ba clauses cannot be used to express two sequentially ordered events that took place in the past. For example:

ドアを開けたら、猫が外に出ました。 Doa o aketara, neko ga soto ni demashita. When I opened the door, the cat went outside.
ドアを開ければ、猫が外に出ました。(ungrammatical) Doa o akereba, neko ga soto ni demashita. (Intended: When I opened the door, the cat went out.)

The following are additional examples of conditionals with a ba clause:

ボタンを押せば、窓が開きます。Botan o oseba mado akimasu. If you press the button, the window opens.
七時になれば、父が帰ります。Shichi-ji ni nareba chichi ga kaerimasu. If (or when) it’s 7 o'clock, my father comes home. (or, Once it's 7 o'clock, my dad returns.)

The ba clause is preferably used to express one’s wishes and regrets, describing what should be or what should have been the desired situation. In this case, the main clause often ends inんです n desu (it is the case that...) or のに no ni (but...). For example:

私がすればよかったんです。Watashi ga sureba yokatta ndesu. I should have done it. (or, It would have been good if I had done it.)
もっと勉強すればいいのに。 Motto benkyō sureba ii noni. I wish I studied more.

. . . と to (whenever, when)

The particle と to follows verbs and adjectives in the plain non-past form. If the main clause is in the non-past tense, the clause with と to only describes a generic condition. Accordingly, the main clause cannot express the speaker’s controllable action, requests, suggestions, permissions, commands, desires, etc. For example:

ロンドンでは冬になると雪が降ります。 Rondon de wa fuyu ni naru to yuki ga furimasu. In London, when it’s winter, it snows.
需要が低いと価格は下がります。Juyō ga hikui to kakaku wa sagarimasu. When the demand is low, the price decreases.

When the main clause is in the past tense, a sentence with と to expresses what happened after doing something, just like a sentence with a tara clause. Thus, the two sentences below are synonymous:

ドアを開けると猫が外に出ました。Doa o akeru to neko ga soto ni demashita.
ドアを開けたら猫が外に出ました。Doa o aketara neko ga soto ni demashita.

I opened the door, and then the cat went out. (or When I opened the door, the cat went out.)

. . . なら nara (if it is the case that . . .)

なら nara can follow verbs and adjectives in the plain form to create a conditional clause (called a nara clause). Note that the non-past affirmative copula だ da must be deleted, and plain past forms are commonly followed by の no when they occur right before なら nara. A nara clause defines the basis of a statement, meaning if it is the case that... or if you are talking about…. For example:

東京に行くなら新幹線がいいですよ。北海道に行くなら飛行機がいいですよ。Tokyou ni iku nara Shinkansen ga ii desu yo. Hokkaidō ni iku nara hikōki ga ii desu yo. If you’re going to Tokyo, the bullet train is good, you know. If you’re going to Hokkaido, the aeroplane is good, you know.
去年北海道に行った（の）なら、今年は九州に行きましょう。 Kyonen Hokkaidō ni itta (no) nara, kotoshi wa kyūshū ni ikimashō. If you went to Hokkaido last year, then let's go to Kyushu this year.

Unlike clauses with tara, ba, and to, a nara clause does not restrict in terms of the relative temporal order of the actions in the clauses in a sentence. The action expressed in a nara clause may take place either before or after the action expressed in the main clause. For example:

パリに行くなら、エッフェル塔をぜひ見てください。Pari ni ikunara, efferutō o zehi mitekudasai. If you are going to Paris, please see the Eiffel Tower (after you get there).
パリに行くなら、ビザを取得してください。Pari ni iku nara, biza o shutoku shite kudasai. If you are going to Paris, please get a visa (before you get there).

Expectedly, a nara clause cannot be used for a temporal condition or a generic condition that expresses what is predicted to happen after some event. Similarly, a nara clause cannot express two sequentially ordered events that occurred in the past. However, a nara clause is most convenient for evaluating facts or expressing intentions, conjectures, suggestions, and requests based on some assumption. For example:

田中さんが行くなら私も行きます。 Tanaka-san ga iku nara watashi mo ikimasu. If Mr./Ms. Tanaka goes, I will go too.
有名な新車なら高いでしょう。Yuumei na Shinsha nara takai deshō. If it's a famous new car, it’s probably expensive.
高橋さんが来ないなら帰りませんか。Takashi-san ga konai nara kaerimasen ka. If Takashi-san doesn’t come, shall we go home?

. . . ても te mo (even if/though, no matter . . . )

A clause that ends in a verb or an adjective in the te form plus the particle も mo forms a concessive clause that means even if... or even though.... For example:

そんなに勉強しなかったんですが、100点は取れませんでした。 Sonnani benkyō shinakattan desu ga, 100-ten wa toremasendeshita. I didn’t study that much, but I couldn’t get a perfect score of 100.
良い本なら高くても買います。Yoi hon nara takakute mo kaimasu. If it's a good book, I'll buy it even if it's expensive.

When such a clause contains a question word, it means no matter…. For example:

どこを探しても見つかりませんでした。 Doko o sagashite mo mitsukarimasendeshita. No matter where I looked, I couldn’t find it.
姉は何を食べても太りません。Ane wa nani o tabete mo futorimasen. No matter what my older sister eats, she doesn’t gain weight.
いくら頑張っても合格できません。Ikura ganbatte mo gokakudekimasen. No matter how much I try, I can't pass.

Permission and prohibition (許可と禁止)

You can express permission by combining a conditional phrase in the form . . . ても te mo (even if . . . ) and an agreement phrase such as いいです ii desu (it is fine). For example, 帰ってもいいです Kaette mo ii desu literally means even if you go home, it is fine, which actually means you may go home.

On the other hand, you express prohibition by combining a conditional phrase in the form . . . ては te wa (if . . . ) and a disagreement phrase such as いけません ikemasen (it is bad). For example, 帰ってはいけません Kaette wa ikemasen literally means if you go home, it is bad, which actually means you may not go home. Permission sentences are often followed by the emphasis particle よ yo to show helpfulness or kindness.

The constructions . . . てもいい te mo ii and . . . てはいけない te wa ikenai can be used not only with verbs but also with a copular verb and adjectives to express minimum conditions, qualifications, or requirements. For example:

浴衣でもいいですよ。Yukata de mo ii desu yo. It's okay even if (you wear) a yukata, you know.
浴衣ではいけません。Yukata de wa ikemasen. Wearing a yukata is not allowed.

Obligation and discretion (義務と裁量)

Obligation is expressed by combining a negative conditional phrase in the form . . . なくては nakute wa (if you do not . . .) and a disagreement phrase like いけません ikemasen (it is bad). For example, 帰らなくてはいけません kaerarakute wa ikemasen literally means if I do not go home, it is bad, which actually means I must go home.

You can express discretion by combining a negative conditional phrase like . . . なくても nakute mo (even if you do not . . .) and an agreement phrase like いいです ii desu (it is fine). For example, 帰らなくてもいいです kaeranakute mo ii desu literally means even if I do not go home, it is fine, which actually means I do not have to go home. For example:

明日までに家賃を払わなくてはいけません。Ashita made ni yachin o harawanakute wa ikemasen. You must pay the rent by tomorrow.
明日は仕事に行かなくてもいいです。 Ashita wa shigoto ni ikanakute mo ii desu. You don’t have to go to work tomorrow.

You can use these obligation and discretion constructions with adjectives and nouns also. For example:

先生でなくてもいいです。Sensei de nakute mo ii desu. You don’t have to be a teacher.
学生でなくてはいけません。Gakusei de nakute wa ikemasen. You must be a student.
社員じゃなくてもいいです。Shain ja nakute mo ii desu. You don’t have to be an employee.
社長でなくてはいけません。Shachō de nakute wa ikemasen. You must be the company president.

Occasionally, . . . なければ nakereba is used instead of . . . なくては nakute wa. For example, 帰らなければいけません kaeranakereba ikemasen and 帰らなくてはいけません kaeranakute wa ikemasen are more or less synonymous, both meaning (I) have to go home. In addition, いけません ikemasen can be replaced with なりません narimasen in this construction. They are almost synonymous, but なりません narimasen gives the impression that the obligatory situation is somewhat inevitable and has arisen naturally. For example:

私は奈良に行かなければなりません。 Watashi wa Nara ni ikanakereba narimasen. I have to go to Nara.