Saying "if" and "when" with the four conditionals

Japanese has many ways to say “if” and provide conditional statements. In this lesson we will introduce the four main ones. Don’t try to memorize this completely, just learn to recognize each of them when you encounter them and know they roughly mean "if" or "when".

The order of conditionals in Japanese states first the condition, and then the resulting action. Conditionals are one way we can connect two “A does B” type sentences in a structure like “If A does B, then C does D”. Obviously, structures like “If A is B, then C does D” or any other combinations are acceptable too.

The first conditional we will see is the ば form which turns verbs into a condition. The conjugation is formed by changing the u at the end of a verb into an e, then adding ば. Basically, for godan verbs, you replace the u with an e, and for ichidan verbs, you add れ after the stem.

見れば死ぬ
If you look you'll die.

こいつを殺せばいいの？
Is it okay if I kill this dude?

ば implies that the condition is sufficient for the result to come to happen. It’s a true logical “if”. This can even be used for certain requests, like "If you're late, just call and I'll handle everything". However, ば doesn't imply that the condition will eventually happen, so it can’t be used in things like "When you come around, come see me". In narration, it can sometimes mean "X happened, and then Y", but this non-conditional usage is fairly limited and not as common outside of literary works.

For the ば conditional of the copula だ, we need to “expand” it into である and conjugate that instead.

普通の人であれば、その命令に逆らうことはできないだろう
If he were a normal person, he surely would not be able to go against that order.

For い adjectives we turn the い into ければ:

良ければ教えてください。
If that is okay (with you), please teach me.

If only it were that simple, with just one conditional, we'd be finished already. But the fun part of Japanese is that there are a lot of different ways to build conditional sentences, and they all have different usages and nuances that are incredibly hard to explain in terms of English grammar. We will now see と, たら, and なら. They all fall into a spectrum of “if” and “when” and sometimes even “as” (like in “As I woke up, I heard a weird sound outside”).

と is used to link two events where one is a natural consequence of the other, in a strongly sequential way.

あんまり食べると太りますよ
If you eat too much, you’ll get fat

This と is also commonly used in narration to describe a series of events that happen one after the other. In this usage, it makes it sound like the reader has no control over the events and they are just a spectator to a show where these events happen “naturally” in front of them.

少し歩くと、開けた場所に出た。
After walking for a while, they came to an open area.

Similar to と, たら is also used to connect two events, and it can either assume a purely hypothetical or a strictly temporal meaning. It can be “If A happens, then B” but also “As A happened, B happened right after”. To more easily make out this distinction, it’s common for phrases in the hypothetical sense to use もし as an opening word to clue in the listener.

もし敵がいたら私が斬り捨てます
In the event that there are enemies, I will cut them down (hypothetical)

朝起きたら、食堂には誰もいなかった。
As I woke up in the morning, there was no one in the cafeteria.

The “as” usage of たら is common when recounting past "one off” events that happened to you, often unexpectedly.

There is another special usage of たら, usually directly after names, in the form of ったら. This ったら has a completely different meaning and just acts as a particle that marks an exclamation of exasperation. It is not a conditional.

もう、お父さんったら、しっかりしなさい！
Come on, dad, get your shit together!

たら and ば in the hypothetical sense can often be interchangeable. There’s even regional variation where people from one area of Japan might prefer one or the other and vice versa. This is why you shouldn’t ask questions like “why did this personr use たら instead of ば?”. Just accept it.

The last conditional for this lesson is なら. なら is a strictly hypothetical conditional. It implies that the condition is assumed true in the hypothetical world where the statement takes place. This means that when you say X なら Y, the meaning is close to something like “If we consider the case that X is true, then Y”, but it doesn't sound as verbose as it does in English. It's a very common way to phrase things.

行きたいなら一緒に行こう
If it’s the case that you want to go, let’s go together

Due to this specific nuance of なら, it is the only conditional where the second clause can happen before the preceding one. と, たら, and ば cannot do this.

乗るなら飲まないで
If you will be driving, do not drink.

The act of 飲む would have to happen before the condition of 乗る, hence the speaker assumes 乗る will happen in the hypothetical world where the advice (飲まないで) takes place.

Sometimes, なら can show up as ならば. The meaning is the same, but it feels more literary.

With verbs and い adjectives, sometimes の can be placed between the verb and なら. This can give some additional nuance (similar to the explanatory の in のだ) but you don't have to remember this. Just remember that the version with の can sound more literary and formal.

そんなに知りたいのなら、教えてあげましょう。
Since you want to know so badly, I shall tell you.

そんなに知りたいなら教えてやる。
Since you want to know so badly, I’ll tell you