We embed questions in sentences all the time by making them subordinate to the main clause, e.g. “I want to know how much money I spent”. In English, we cannot just insert the question we want to know directly into the sentence: the grammar does not allow us to do this. In other words, we cannot do the following:
“I don’t know” + “What did he say?”
I don’t know what did he say. (✘)
I don’t know what he said. (✔)
→ The form of the verb “to say” changes.
“I’m wondering” + “What should I take on holiday?”
I’m wondering what should I take on holiday. (✘)
I’m wondering what I should take on holiday. (✔)
→ The order of “should” and “I” changes.
Japanese grammar lets us merge questions without thinking about word order. In other words, in Japanese we can say the following as one sentence:
“What did he say(?) I don’t know”
“What should I take on holiday(?) I’m wondering”
We must, however, remember two rules:
Take these two separate sentences.
| I don’t understand 〜 |
| What did he say? |
Let’s just go ahead and throw the second sentence directly into the「〜」in the first.
私は彼は何を言いましたかがわかりません。(✘)
First we need to put the embedded question clause in the standard form:
私は彼は何を言ったかがわかりません。(✘)
Then we need to use the subject particle to link “he” with the verb “to say”.
| I don’t understand what he said. |
In most cases (and practically 100% of cases for spoken Japanese), the particle that follows the embedded question clause is omitted—in this case, the が particle.
| I don’t understand what he said. |
| 電車が何時に出発するか（を）調べます。 |
| I’ll find out what time the train departs. |
The above rules work perfectly when you have a question word like “what” (何) or “what time” (何時). But what if there is no question word? To embed a “Yes/No” question (translating to “whether or not” or “if” in English), we add どうか after the question particle か.
| 明日 雨が 降るかどうか わかりません。 |
| I don’t know whether or not it will rain tomorrow. |
| その映画が 面白いかどうか わかりません。 |
| I don’t know whether or not that film is interesting. |