I've been reading Minna-no-nihongo and I came across examples:



  1. For some reasons I thought that an idea or opinion expressed with と思う had to be in informal form. But in those particular examples there are です and ます. Even if I was wrong and you can use polite form there then why one clause is in polite form and other is in inpolite one? Shouldn't two coordinated clauses be in agreement regarding politeness? So, question is:

What is the rule for politeness level with と思う? Something like 'you should put in polite form only the last clause preceding the と思う' or something like that.

  1. I was thinking that one option to explain it grammatically is that と思う in those examples refering only to second clause. So, it's not

I think that they study well but don't read much.

but more like:

They study well, but I think they don't read much.

If that's the case then is it possible to use:


with the meaning: "I think that they study well but don't read much", where all the expression preceding と思う is my opinion?

  • Could you specify where you found these examples, for example which chapter of which edition (etc.)? Commented Jul 14, 2020 at 11:07

1 Answer 1


Basically, yes - you only need to put the last clause, the bit ending right before the と of と思う, in plain form. It doesn't strictly have to be in plain form, either, but it sounds much more natural to do so, unless you're trying to sound extra-polite.

But I also think that your argument that only a portion of the sentence is being "quoted" by the と is also a valid way of thinking about it, at least in some cases. Certainly, I feel that "They study well, but I think they don't read the book" is a more natural translation of the above than "I think they study well but don't read the book". However, I don't think reducing the します to する would be the appropriate way to indicate that - it wouldn't convey that inclusion any more clearly, but would just reduce the overall level of politeness/formality.

Instead, I think it'd be more natural to just state the thought completely, and then follow it with "Or anyway that's what I think." 彼らはよく勉強しますけど、本を読みません。まあ、そうと思いますけどね。(But if I'm being honest, I don't think either this version nor the original sound very close to something an actual native Japanese person would express - it's more "textbook Japanese".)

Note that while people often speak of 読みます being "the -ます form of 読む", the reality is that ます was originally just an auxiliary/helper verb with no particular meaning (that I'm aware of), added for the purpose of expressing politeness or deference. In regular Japanese 丁寧語, it mostly suffices to pepper in at the ends of major clauses. You don't use it in modifying clauses, and really the reason why you don't use it before the と of と思います is really just because you're already using -ます for the 思う, so you don't need to use it twice so close together. At least, that's how I think about it, dunno how valid it is.

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