particle
question marker, or, whether
1. question marker
Placed at the end of a sentence to form a question. With polite forms, rising intonation is optional; with plain forms, rising intonation is typical.
これは(なん)ですか。
What is this?
明日(あした)()ますか。
Are you coming tomorrow?
日本語(にほんご)()かりますか。
Do you understand Japanese?
2. or (between options)
Used between nouns or clauses to present alternatives.
コーヒーか紅茶(こうちゃ)
coffee or tea
()くか()かないか、()めてください。
Please decide whether you're going or not.
3. whether, if (embedded questions)
Marks embedded questions, equivalent to 'whether' or 'if' in English.
(かれ)()るかどうか()からない。
I don't know whether he's coming.
(なに)()ったか(おし)えてください。
Please tell me what you bought.

か is the primary question-forming particle in Japanese.

MAIN USES:
1. Yes/No questions: ()きますか (Are you going?)
2. WH-questions: (なん)ですか (What is it?)
3. Alternative questions: AかB (A or B)
4. Embedded questions: ...かどうか (whether...)

PATTERNS:

  • Sentence + か: direct question
  • A か B: A or B
  • Verb/Adj + か + どうか: whether or not
  • Question word + か: embedded question

NOTE: In casual speech, か may be omitted and replaced by rising intonation alone. In very casual male speech, か can sound blunt.