I think it’s fair to say that all modern languages (which the exception of those constructed by academics) grow and evolve in response to the times and the culture of the countries speaking those languages. This means that there aren’t many hard and fast rules that work 100% of the time. It’s almost as if exception itself is the only rule.
One of my favorite examples of this in English are the particles “the” and “a”. If you were asked to explain their meaning to someone, you might start with “Well, ‘the’ is used for specific things, and ‘a’ for non-specific things…”, and while there is some truth to that, the real story is much more complex, riddled with exceptions. (This page has the basics, but there are some cases not listed there).
So the job for those trying to boil down the grammar of a language to a simple set of rules is quite difficult, whether you are writing a textbook, teaching a class, or writing a language learning blog. What typically happens is that the easily explainable, most useful bits of grammar are taught first, in a simplified form without mentioning every possible detail. This is as it should be, since otherwise beginners will get frustrated with the complex set of rules and exceptions they have to memorize from day one.
However, the more you learn a language, the more you start getting the basics and desire more of the nitty gritty – knowledge that only fluent speakers know. It’s natural to try and learn these tricker areas of a foreign language through daily exposure. After all, if you hear something enough times it will eventually stick, and when you speak hopefully you’ll use the same structures and usages that you heard.
But personally, being so grammar-based I tend to want to see it all written out, with the long list of rules and exceptions. Only then can I begin to feel more comfortable about my knowledge of a language’s grammar.
Sorry about the long introduction but we’ve finally come to the main attraction for this article – conditionals in Japanese. Here I am using the word conditional in a very loose sense to refer to these three grammatical forms: したら、すると and すれば. Depending on the context these can be also called suppositional. I gave the する conjugations for each of these three for simplicity (instead of saying “たら と ば” as some study materials), but make sure you understand I am referring to all verbs in a generic sense, not just する。
I’m not going to discuss the verb conjugation rules for these three forms, and will assume you have at least a basic familiarity with them. You’re likely to hear about this trio in Japanese textbooks or websites, but I have never found a source in English which goes into great detail about the difference between the three, so I felt there was a need for this article.
The simplest way to explain what is common between these three structures is that they all can be used to express the concept of “if” or “when”. Let’s look at some example sentences.
- If you eat a lot, you’ll feel better.
For this example, I feel that all three sentences are quite natural and have nearly the same meaning.
Now we get to the sticky part. Even though these three forms can be used in the same way, they also have little quirks of their own. For example, there are some cases where using one of the forms is natural, but using another one is awkward or just plain wrong.
First, it’s good to know that したら is the most flexible form and works for almost all usages (except for #2 and #6 below). If you aren’t sure which of the three to use, it’s probably safest to try this.
Before I go over each specific usage, I’d like to discuss the major conceptual differences between すると、したら、and すれば. Knowing these will help you understand the reasoning behind each specific usage.
This form is typically used to describe concrete facts or to talk about things which occur out of necessity (cause/effect relationship). It is also used for customary or habitual actions. The most common usage of this is discussed below in Usage 6.
The fact that there is a implication of certainty or objectivity when すると is why it is not used for things like commands, permission, or desire-related statements, as discussed in Usage 5 below.
したら is commonly used for statements that have an emphasis on individuality (something subjective, i.e. related to a person) or a coincidental event. This reflects on Usage 5 below.
While it can be used for inferences (“I think if X happens, then Y will occur”), in conversation すれば is used more frequently for these.
The most important thing to know about すれば is that it is generally used to represent imagined situations which have not yet occurred. This is covered by both Usages 1 and 4 below.
Now I’ll go over each usage and discuss which forms are appropriate for that usage.
Usage 1: Basic if/when conditional, where the verb on the right side is in the basic non-past form (i.e. する).
All three forms (したら、すると、すれば）can be used for this. The first set of sentences above (about eating) fall into this category.
Usage 2: Simple connections, when the first part of the sentence is only introducing the latter part
In this case there is no sense of time order between the two parts of the sentence.
- According to the teacher, today’s class is cancelled.
Here the すると and すれば forms are natural, but したら (よったら) is unnatural. This usage is called 単純接続 in Japanese (“simple connection”).
I feel this use is pretty rare, and off hand I can’t think of any other examples, but I’ve included it for completeness.
Usage 3: The verb of the right side is in the past tense and actually happened.
- When I swam I got tired.
Here only the したら (泳いだら) form is natural since the verb 疲れた is in the past tense and actually occurred.
Usage 4: The verb on the right side is in past tense but didn’t happen.
An example of this usage is when you are complaining to or admonishing someone. The verb on the right side could have happened, but didn’t because some condition wasn’t fulfilled.
- You should have gone together with me. (It would have been good if you went together with me)
Here we can see the すると (くれると) form is inappropriate. To me the final sentence here (くれれば) sounds the most natural and is what I would use in conversation, though using くれたら is also correct.
Usage 5: Sentence that express a command, desire, or permission.
- When you arrive please contact me.
Here only したら(着いたら) is valid since this is a command and hence has a subjective element . Sentences that end in 〜なさい、〜ください, 〜していい, 〜したい, ~つもり would fall into this category. Sentences like “そうすればいいじゃないか” where someone is trying to convince someone of something would also only work with the すれば form.
Usage 6: Describing an inevitable result of a predictable event, including acts of nature.
- When spring comes, the flowers bloom.
Here only the すると (なると) form is seen as natural.
This usage is the most confusing because it’s hard to distinguish from the Usage 1 above, where any of the three forms can be safely used. If you search for the above sentences on Google (make sure you use double quotes), you’ll find a few hits even for the “wrong” ones, so it seems that even Japanese people may mistake this form on occasion.
The form is said to be used often for “natural occurrences” (自然現象), such as the example sentence I used above which sounds like it came from a poem. I have a children’s book on tomato growing and the すると form is used several times in it.
My general feeling is the すると form is the least used of these three, especially in everyday conversation. When used in books sometimes I feel it has a dramatic tone, as in the phrase “すると。。。” (And then….)
1) I heavily used the first four references below (all in Japanese). If you want to get even more details, feel free to check them out.
2) The first link below is especially interesting as it shows a Japanese person trying to analyze several sources of information on this topic. At some points he actually criticizes the relevant Goo Dictionary database entry, and comes to the conclusion that there are certain exceptions he hasn’t been able to fully understand.
3) The word なら can be used after noun or a verb and can be used to mean “if” as well. However I’ve omitted it in this discussion in order to try and keep this difficult topic as simple as possible.