The question marker is covered here because it is primarily used to clearly indicate a question in polite sentences. While it is entirely possible to express a question even in polite form using just intonation, the question marker is often attached to the very end of the sentence to indicate a question. The question marker is simply the hiragana character 「か」 and you don't need to add a question mark. For previously explained reasons, you must not use the declarative 「だ」 with the question marker.
田中さん：お母さんはどこですか。
Tanaka-san: Where is (your) mother?
鈴木さん：母は買い物に行きました。
Suzuki-san: (My) mother went shopping.
キムさん：イタリア料理を食べに行きませんか。
Kim-san: Go to eat Italian food?
鈴木さん：すみません。ちょっと、お腹がいっぱいです。
Suzuki-san: Sorry. (My) stomach is a little full.
Here the question is actually being used as an invitation just like how in English we say, "Won't you come in for a drink?" 「すみません」 is a polite way of apologizing. Slightly less formal is 「ごめんなさい」 while the casual version is simply 「ごめん」.
It makes sense to conclude that the question marker would work in exactly the same way in casual speech as it does in polite speech. However, this is not the case. The question marker 「か」 is usually not used with casual speech to make actual questions. It is often used to consider whether something is true or not. Depending on the context and intonation, it can also be used to make rhetorical questions or to express sarcasm. It can sound quite rough so you might want to be careful about using 「か」 for questions in the plain casual form.
Instead of 「か」, real questions in casual speech are usually asked with the explanatory の particle or nothing at all except for a rise in intonation, as we have already seen in previous sections.
Another use of the question marker is simply grammatical and has nothing to do with the politeness. A question marker attached to the end of a subordinate clause makes a mini-question inside a larger sentence. This allows the speaker to talk about the question. For example, you can talk about the question, "What did I eat today?" In the following examples, the question that is being considered is in red.
In sentences like example 3 where the question being considered has a yes/no answer, it is common (but not necessary) to attach 「どうか」. This is roughly equivalent to saying, "whether or not" in English. You can also include the alternative as well to mean the same thing.
While we're on the topic of questions, this is a good time to go over question words (where, who, what, etc.) and what they mean in various contexts. Take a look at what adding the question marker does to the meaning of the words.
| Word+Question Marker | Meaning |
|---|---|
| 誰か | Someone |
| 何か | Something |
| いつか | Sometime |
| どこか | Somewhere |
| どれか | A certain one from many |
As you can see by the following examples, you can treat these words just like any regular nouns.
The same question words in the chart above can be combined with 「も」 in a negative sentence to mean "nobody" （誰も）, "nothing" （何も）, "nowhere" （どこも）, etc.
「誰も」 and 「何も」 are primarily used only for negative sentences. Curiously, there is no way to say "everything" with question words. Instead, it is conventional to use other words like 「全部」. And although 「誰も」 can sometimes be used to mean "everybody", it is customary to use 「皆」 or 「皆さん」
The remaining three words 「いつも」 (meaning "always") and 「どれも」 (meaning "any and all"), and 「どこも」 (meaning everywhere) can be used in both negative and positive sentences.
| Word+も | Meaning |
|---|---|
| 誰も | Everybody/Nobody |
| 何も | Nothing (negative only) |
| いつも | Always |
| どこも | Everywhere |
| どれも | Any and all |
(Grammatically, this 「も」 is the same as the topic particle 「も」 so the target particle 「に」 must go before the topic particle 「も」 in ordering.)
The same question words combined with 「でも」 can be used to mean "any". One thing to be careful about is that 「何でも」 is read as 「なんでも」 and not 「なにでも」
| Word+でも | Meaning |
|---|---|
| 誰でも | Anybody |
| 何でも | Anything |
| いつでも | Anytime |
| どこでも | Anywhere |
| どれでも | Whichever |