I understand that ことになる has the meaning "It has been decided that" and can be used to point to a ritual or habit of a society like taking off your shoes.

However, I don't get what it means when it is like this:


How is that different from say,



3 Answers 3


First, I must clearly state that "it has been decided that ~~" is a highly overrated translation of 「~~ことになる」 among J-learners. Truth is that that is not what it means even half the time.

「あすで1週間雨{しゅうかんあめ}が降{ふ}りつづくことになる。」 means "It will have ended up raining a whole week." It has already been raining for 6 straight days now (at the time of utterance) and the weather forecast says that it will rain again tomorrow.

A more natural or less stiff way to say this would be 「もし明日{あす}も雨だったら、(これで)一週間雨が降り続{つづ}いたことになる。」, but virtually all native speakers would understand 「あすで1週間雨が降りつづくことになる。」.

Here, 「ことになる」 means "to end up (in a certain way)" and that is already a very common usage of the expression.

Your second sentence 「あすで1週間雨が降りつづくようになる。」, however, makes little sense, I am afraid.

「ことになる」 refers to (and focuses on) the final result whether it happened naturally or someone made it happen on purpose.

「ようになる」 focuses on the change from one situation to another. "It was like A before but it is like B now." e.g. 「去年{きょねん}までは泳{およ}げなかったが、今年{ことし}からは泳げるようになった。」 In this example sentence, you cannot replace the 「ようになった」part with a 「ことになった」 because it talks about a change in one's swimming ability.


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    Quote formatting for text which is not actually a quote is confusing. Commented Jul 25, 2014 at 16:31
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    Brilliant! I had the same feeling that that translation was overrated. I only used it as a reference point. I'm the same way with most translations and explanations of Japanese. It's not a really well dealt with language compared to other ones. I understand now though. The よう one focuses on a change from one situation to another and the こと one is only a descriptor of the final result at that point in time.
    – Nathan
    Commented Jul 25, 2014 at 22:48
  • @Tim: I'm not talking about the 「」but about the blockquote (yellow background box). However, you can also mark Japanese text with backticks. (The link also mentions using blockquote, but for fragments of Japanese text). Commented Jul 26, 2014 at 1:07
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    Well, @Brandon's answer could be using blockquote and it would look fine. The issue in this one is that it mixes example text with explanation in the quote block. Commented Jul 26, 2014 at 1:10

1週間雨が降りつづくことになる。 is totally fine.
"it will end up raining for a week"
1週間雨が降りつづくようになる。 is very strange.
"it will come to be that it rains for a week"
1週間雨が降りつづくようだ。 is fine.
"it appears that it will rain for a week"

Using user1713450's pizza example:

"I decided to eat pizza"
"I ended up eating pizza"
"I came to eat pizza"
"I made an effort to eat pizza"


Where did you see the first example? It doesn’t make sense to me unless you believe in the Greek gods and are saying it has been decided (by them) that it will continue to rain.

The verb that precedes ことになる must be one that is capable of being decided and done. Natural phenomena out of the hands of human beings, cannot ことになる.

You are likely getting confused because in English, “to decide” can mean either “decide to take an action” or “decide some fact will come to pass.”

In the case of it continuing to rain, this would be a decision (conclusion, actually) that some fact will come to pass. This is not what you use ことになる for. You use it for the “decide to take an action” one.

Think of ことになる as a passive form of ことにする

ピザを食べることにした = I decided to eat pizza. ピザを食べることになった = It was decided that (we/I/he) would eat pizza.

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    The first two paragraphs make no sense. OP's first sentence is alright. It is something native speakers say quite often.
    – user4032
    Commented Jul 25, 2014 at 15:04
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    Please ensure you are fluent or very well versed in Japanese before you advise learners, particularly if you have a teaching style where you almost insult the learner by confidently telling him how weird his Japanese is, even when it is perfectly fine. If you have an idea, you can tentatively raise it so long as you first stipulate that you don't really know at all, and that you are just wanting to see if you are correct or not. Some examples of good openers that suit you: "My Japanese is not very good but I think..." "I'm only a beginner, but..." "Could someone who is good explain to me..."
    – Nathan
    Commented Jul 25, 2014 at 22:51

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