か: 'Or' and Indefinite (誰か, どれか) | Japanese Grammar

You already know か as the question particle that turns a statement into a question. What looks at first like a second, unrelated か — the one that means "or," and the one hiding inside 誰か (someone) and 何か (something) — is really the same か doing the same job. The thread running through all of them is uncertainty: a question leaves the answer open, "or" leaves the choice open, and "some-" leaves the identity open. Once you see that thread, the whole system stops feeling like a pile of separate rules and starts feeling like one idea wearing three hats.

か as "or": joining alternatives

Placed between two nouns, か means "or." It offers a set of alternatives and leaves open which one applies.

コーヒーか紅茶、どっちがいい？

kōhī ka kōcha, dotchi ga ii?

Coffee or tea — which would you like?

バスか電車で行きます。

basu ka densha de ikimasu

I'll go by bus or train.

土曜か日曜に会いましょう。

doyō ka nichiyō ni aimashō

Let's meet on Saturday or Sunday.

You can chain more than two: 赤か青か緑 (red or blue or green). Note that in バスか電車で, the particle で ("by means of") attaches once, at the end of the whole group — か binds the nouns together tightly, and the case particle wraps the bundle.

This is the casual, everyday "or." Japanese does have a more formal written "or," または, but it belongs to documents, forms, and announcements — not to talking about lunch. Reaching for または in conversation sounds stiff and bureaucratic, the way saying "coffee or, alternatively, tea" would in English.

You can also offer a choice by stacking two full か-questions instead of joining the nouns — コーヒーですか、紅茶ですか ("Coffee? Or tea?"). That version spells out each option as its own polite question and is common when a waiter or host is presenting alternatives one by one; the compact コーヒーか紅茶 is what you'd use among friends.

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For "or" between nouns in ordinary speech, use か. Save または for formal writing — signs, contracts, instructions ("記入は黒か青のペンで" is natural speech; "黒または青のインク" is form-speak).

か vs や vs と: three ways to list

English uses "and" and "or" and leaves it at that, but Japanese splits noun-listing into three particles, and か is the "or" of the set. Keeping all three straight prevents a common muddle:

Particle	Meaning	Example
と	"and" — exhaustive (these and only these)	りんごとバナナ — apples and bananas (just those two)
や	"and" — non-exhaustive (these, among others)	りんごやバナナ — apples, bananas, and so on
か	"or" — alternatives (one of these)	りんごかバナナ — apples or bananas

昼ご飯はパンかおにぎりでいい。

hirugohan wa pan ka onigiri de ii

For lunch, bread or a rice ball is fine.

The trap is reaching for と or や when you mean a choice. パンとおにぎり is "bread and a rice ball" (you'll have both); パンかおにぎり is "bread or a rice ball" (one of them). Only か expresses the either/or.

か … か: "whether … or …"

Put か after each of two contrasting verbs and you get "whether X or Y," laying out both possibilities explicitly. The most common pairing is a verb against its own negative:

行くか行かないか、早く決めて。

iku ka ikanai ka, hayaku kimete

Decide quickly whether you're going or not.

本当か嘘か、私には分からない。

hontō ka uso ka, watashi ni wa wakaranai

Whether it's true or a lie, I have no idea.

Indefinites: question word + か = "some-"

Here is where the "uncertainty" idea pays off most. Attach か to a question word and you get an indefinite — a "some-" word that names a member of the set without specifying which one. The question word says which kind of thing (person, thing, place, time); か says some unspecified one.

Question word	か	Meaning
誰 (who)	誰か	someone
何 (what)	何か	something
どこ (where)	どこか	somewhere
いつ (when)	いつか	sometime, someday
どれ (which one)	どれか	one of them, some one
どちら (which of two)	どちらか	one of the two, either

何か食べたい。

nanika tabetai

I want to eat something.

誰かが玄関にいるよ。

dareka ga genkan ni iru yo

There's someone at the front door.

また、いつか会いましょう。

mata, itsuka aimashō

Let's meet again sometime.

この中のどれか一つ選んでください。

kono naka no doreka hitotsu erande kudasai

Please pick one of these.

Notice the particle behaviour in 何か食べたい: after 何か and 誰か, the object marker を and subject marker が are very often dropped in casual speech. 何か食べたい is far more natural than 何かを食べたい; both are grammatical, but the shorter one is what people actually say. When the indefinite is a subject, が can appear (誰かが来た) or drop (誰か来た) — both are fine.

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Think of it as a set-with-a-question-mark. 誰 = "who?" (the whole set of people, identity unknown). Add か and you answer the question vaguely: "some (one) person." The same か that opens the question closes it with an unspecified value. That is why 誰か means someone — it is literally "some who."

The +か / +も / +でも family

か is one of three particles that pair with question words, and seeing all three together makes each one click:

Base	か (some)	も (with negative: none)	でも (any)
誰	誰か — someone	誰も…ない — no one	誰でも — anyone
何	何か — something	何も…ない — nothing	何でも — anything
どこ	どこか — somewhere	どこも…ない — nowhere	どこでも — anywhere

か marks some (unspecified but existing), も with a negative marks none, and でも marks any (free choice). The full paradigm — including the tricky も cases — is drilled on the question word + か / も / でも page.

Embedding a question: 〜かどうか

か's uncertainty even lets it swallow an entire question and slot it inside a bigger sentence. 〜かどうか ("whether or not") turns a yes/no question into a noun-like chunk that can be the object of verbs like 分かる (know), 知る (find out), or 覚えている (remember).

彼が来るかどうか、まだ分からない。

kare ga kuru ka dōka, mada wakaranai

I don't yet know whether or not he's coming.

この水が飲めるかどうか確認してください。

kono mizu ga nomeru ka dōka kakunin shite kudasai

Please check whether this water is drinkable.

For a wh-question embedded the same way (どこに行くか分からない — "I don't know where he's going"), か attaches directly without どうか. The full syntax of embedded questions gets its own page: embedded questions with かどうか.

Common Mistakes

❌ コーヒーまたは紅茶、どっちがいい？

Too stiff for conversation — または is formal/written 'or'; use か when chatting.

✅ コーヒーか紅茶、どっちがいい？

kōhī ka kōcha, dotchi ga ii?

Coffee or tea, which would you like?

❌ 何食べたい。（「何か食べたい」のつもりで）

This means 'What do you want to eat?' — without か it's a question word, not 'something.'

✅ 何か食べたい。

nanika tabetai

I want to eat something.

This is the single most common か-indefinite error. 何 is what (a question); 何か is something (a value). Drop the か and "I want something to eat" collapses into "what do you want to eat?" — the exact opposite of a statement.

❌ 行くどうか、まだ分からない。

Missing か — 'whether or not' is かどうか, not どうか alone.

✅ 行くかどうか、まだ分からない。

iku ka dōka, mada wakaranai

I don't know yet whether I'll go.

❌ 部屋に誰も来た。（「誰かが来た」のつもりで）

誰も + affirmative is wrong for 'someone came'; 誰も pairs with a negative for 'no one.'

✅ 部屋に誰か来た。

heya ni dareka kita

Someone came into the room.

か is for some (誰か = someone); も is for none and needs a negative verb (誰も来なかった = no one came). Swapping them flips the meaning entirely.

Key Takeaways

One か, three jobs: question (open answer), "or" (open choice), "some-" (open identity) — all united by uncertainty.
Between nouns, か = casual "or"; または is the formal/written equivalent, out of place in speech.
Question word + か = "some-" (誰か someone, 何か something, いつか sometime); the object marker を usually drops after them.
何 is what; 何か is something — the か is not optional decoration, it changes the part of speech.
〜かどうか embeds a yes/no question ("whether or not") as the object of verbs of knowing.

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