Here is a multiple-choice question from my grammar exercise book. I can rule out all but two choices below.

医者の話では、2ヵ月ぐらいで退院できるだろう__。(a.そうだ b.ということだ)

The correct answer according to the book is “b.ということだ”, but is “a.そうだ” incorrect?

Edit: The relevant section of the book covers ということだ but not そうだ.

  • 1
    Did the book say that だろうそうだ is a possible grammar construction? Usually there's a section that tells you what parts of speech can connect to the grammar elements.
    – Leebo
    Mar 5, 2021 at 10:03
  • 1
    @Leebo The book didn’t say anything particular about そうだ. Another source that I could find says the construction is “plain form + そうだ”. I suppose だろう would count as plain form, in contrast with the polite form でしょう?
    – Cabbage
    Mar 6, 2021 at 4:01
  • @Cabbage That information is important for us to know where the question's focus is. Could you incorporate it into your question body? Mar 8, 2021 at 4:50

1 Answer 1


~だろう already indicates hearsay, so adding another layer of hearsay (そうだ) to it makes it sound incredibly awkward.

The concept is similar to how you can't add the word "didn't" to verbs already in the past tense (i.e. "didn't saw") in English.

You can however, conjoin そうだ to だ giving you something like this:


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