I've been trying to figure out the difference between だろうか and のだろうか through context in my reading, but it's proving harder than I thought. Here's a passage with both. What is the difference, and why are each used in their respective sentences? If I'm assuming it's the explanatory の, then I think のだろうか has more of an inquiry/worried/wondering feeling than just plain だろうか, but I'm not completely sure.


1 Answer 1


Yes, that の is an explanatory-の, and it has to be used when the preceding phrase serves as an explanation for something. Here, this person is comparing two possible reasons, or explanations, for the frightened look (i.e., 私は紅魔族だ versus 私に貫禄がでてきた). So either から or の is necessary in the last sentence.

Is this because I am a Crimson Demon? Or is it {because|that} I've finally started to gain an aura as an adventurer?

In the last sentence, it's okay to omit "because" and just say "Or have I started to gain..." in English. In Japanese, の is used very often, and it's almost mandatory to explicitly use の (or から) here. But in the other sentence, there is already から, so adding の is not necessary (although it's also fine to use both and say "紅魔族だからなのだろうか").

  • Thank You! Side Question, on this Bunpro article, it says that だろうか must be nominalized. Does the の act as both a nominalizer and an explanatory particle?
    – shawntarou
    Feb 17 at 7:34
  • 1
    @shawntarou Etymologically, だ in だろう seems to be the copula (だ as in 彼は学生だ), but now it can safely take the 終止形 of a verb directly, without nominalization. It's perfectly natural to say 彼は来るだろう, 彼はその時そこにいただろう, etc.
    – naruto
    Feb 17 at 8:58

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