か(ka) — Question, Or, and Uncertain Identity

• それは本当ですか？

  Sore wa hontou desu ka?

  Is that true?

  Statement + か turns it into a yes/no question

• ペンか鉛筆を貸してください。

  Pen ka enpitsu o kashite kudasai.

  Please lend me a pen or a pencil.

  か between nouns means 'or'

• 誰か来ましたか？

  Dareka kimashita ka?

  Did someone come?

  誰 (who) + か = 誰か (someone); the final か makes it a question. Not to be confused with 誰が (who specifically).

• ・Question Words + か: 何か (something), 誰か (someone), どこか (somewhere), いつか (sometime).
• ・Embedded Questions: You can embed a question inside a sentence with か: いつ行くか分かりません (I don't know when I'm going).
• ・Nuance: In casual speech, '行くか？' to a friend can sound blunt or masculine; a softer casual question just uses rising intonation without か.

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones か is tested against.

• は (wa) — Topic & Contrast Particle
• が (ga) — Subject Marker & Exhaustive Listing
• を (o) — Direct Object & Traversal
• に (ni) — Target, Time, and Existence Location
• で (de) — Context of Action (Location, Means, Condition)
• と (to) — And (Exhaustive), With, and Quotation
• の (no) — Possession, Modification, & Nominalization
• も (mo) — Also, Too, Both/And, Emphasized Quantity