Sentence-final particle indicating a question (asks or seeks confirmation).
これは君のペンか。
Is this your pen?
明日行けますか。
Can you go tomorrow?
彼が学生かどうか教えてください。
Please tell me whether he is a student or not.
Used after each alternative to mean 'or' / 'whether' (as in X ka Y ka).
コーヒーか紅茶か、どちらがいいですか。
Coffee or tea — which do you prefer?
バスか電車かで行く予定です。
I plan to go by bus or by train.
肉か魚か、好きな方を選んでください。
Choose either meat or fish.
Used after interrogatives (何・誰・どこ, etc.) to form indefinite expressions like 'something' or 'someone' (e.g., 何か = something).
何か手伝いましょうか。
Shall I help with something?
誰か来たか？
Did someone come?
どこか行きたい場所はありますか。
Is there somewhere you'd like to go?
An utterance-like 'ka' expressing hesitation, doubt, or uncertainty; used to trail off or show the speaker's unsure attitude.
彼が本当に来るか…分からない。
Whether he'll really come... I don't know.
そんなことが起こるか、と彼は呟いた。
He murmured, 'Could such a thing happen?'
Prefix meaning 'very' or 'exceedingly' used before adjectives (often literary), as in か弱い (very weak/frail).
か弱い少女が静かに座っていた。
A very frail girl sat quietly.
か細い声で彼女は名前を呼んだ。
She called the name in a very thin (weak) voice.
Suffix forming adjectives/adverbs (similar to English -al/-ic/-ish/-y), as in 定か (clear/certain).
彼の記憶は定かではない。
His memory is not clear.
事件の真相は未だ定かでない。
The truth of the incident is still uncertain.
Archaic/adverbial use meaning 'in that way' or 'thus' (found in classical/literary Japanese; rare in modern usage).
文語では、『か』が『そのように』の意味で用いられることがある（例は古い書き言葉に見られる）。
In classical written Japanese, 'か' is sometimes used to mean 'in that way' (this usage appears in old texts).