のだろうか
I wonder...
Structure
［い］Adjective +（の(1)）+ だろうか
［な］Adjective +（な + の(1)）+ だろうか
Noun +（な + の(1)）+ だろうか
(1) ん
Explanation
When the conjugated auxiliary verb だろう is combined with the question particle か, it conveys the speaker's speculation or uncertainty about the preceding statement. In English, this is often equivalent to the phrase 'I wonder if...'.
Grammatically, the clause that comes before だろうか is required to be nominalized, meaning it must be converted into a noun phrase. This is accomplished by adding の, or by using なの in the case of な-Adjectives and nouns.
- 明日は晴れるのだろうか。I wonder if it will be sunny tomorrow.
- この映画は面白いのだろうか。I wonder if this movie is interesting.
- 山田さんは元気なのだろうか。I wonder if Mr. Yamada is doing well.
- これは本物なのだろうか。I wonder if this is the real thing.
Although the nominalizing の (or なの) is technically required by the rule, in common usage it is frequently dropped from the phrase.
- 彼は時間どおりに来るだろうか。I wonder if he will come on time. (の omitted)
- あの人は本当に学生だろうか。I wonder if that person is actually a student. (なの omitted)
だろうか can have a somewhat masculine nuance. To express a more polite or gender-neutral feeling, でしょうか is often used as an alternative.
- 会議は時間どおりに終わるのでしょうか。I wonder if the meeting will end on time.
- この建物は図書館なのでしょうか。I wonder if this building is a library.
Caution
While だろうか can feel masculine, it's important to note that でしょうか is not strictly feminine. でしょうか is a neutral, polite form that can be used comfortably by any speaker.
Fun Fact
Much like だろう, the phrase だろうか can serve either to pose a question to another person or to simply voice the speaker's own internal musings.
- 彼の話は本当なのだろうか。I wonder if his story is true. (Said while talking to oneself)
- このケーキを食べていいのだろうか？I wonder if it's okay for me to eat this cake. (Said while talking to oneself)
However, だろうか is most frequently used to convey a personal sense of wonder, much like かな. Because of this, even when directed at someone, the listener might perceive it as the speaker just thinking out loud, rather than asking a question that requires an answer.
Examples
この料理は本当に美味しいだろうか。
I wonder if this dish is really delicious.
あの人は学生だろうか。
I wonder if that person is a student.
明日は晴れるだろうか。
I wonder if it will be sunny tomorrow.
バスは時間通りに来るだろうか。
I wonder if the bus will come on time.
彼はわたしのことを覚えているのだろうか。
I wonder if he remembers me.
このボタンを押してもいいのだろうか。
I wonder if it's okay to press this button.
まだ仕事がたくさん残っているけど、もう帰っていいのだろうか。
There's still a lot of work left, but I wonder if it's okay to go home now.
どうして彼はあんなに怒っているのだろうか。
I wonder why he is so angry.
このプレゼント、彼女は喜んでくれるのだろうか。
I wonder if she will be happy with this present.
鍵をかけたはずなのに、ドアが開いている。誰かが入ったのだろうか。
I'm sure I locked it, but the door is open. I wonder if someone came in.
テストはとても簡単だったので、満点を取れるのだろうかと思った。
The test was very easy, so I wondered if I could get a perfect score.
初めて日本に来た時、言葉も文化も分からなかった。ここで一人で生活できるのだろうかと思った。
When I first came to Japan, I didn't understand the language or the culture. I wondered if I would be able to live here alone.