か

1. 1Marks a sentence as a question, either yes/no or with a question word such as 何.Ex. 1
2. 2Placed after each option in an alternative question to ask which one the listener chooses.Ex. 2

The basic question marker, used in speech and writing, most often after polite です/ます forms. In casual speech, questions are usually made with rising intonation alone, since plain form + か can sound blunt. かどうか embeds a yes/no question inside a larger sentence, and それとも links two alternative questions as 'or'.

• か〜かN5「か〜か」puts two options (nouns, verbs, etc.) into one sentence, often paired with 「どちら」, or forms an indirect question followed by verbs such as 「決める」 or 「分かる」. Sentence-final 「か」 asks directly; when choosing between alternatives you place two complete questions side by side.
• かどうかN4「かどうか」 is not used to ask at the end of a sentence; instead it embeds a yes/no question without a question word into a sentence as the content of verbs like 「分かる」 or 「確認する」, meaning 'whether'. Clauses containing a question word use 「か」, not 「かどうか」.
• それともN3「それとも」 relates only to the alternative-question sense of 「か」. In 「〜か、〜か」 the particle simply lists options side by side, while 「それとも」 sits between two questions to explicitly offer another option; they are largely interchangeable and often used together. 「それとも」 cannot form ordinary yes/no questions.
• かいN4「かい」 is colloquial only, attaches to plain forms, and sounds softer and friendlier than plain-form plus 「か」, typically used with familiars or juniors. It mainly asks yes/no questions or serves rhetorical effect; with a question word 「だい」 is more common, and it should be avoided in polite situations.
• かしらN4「かしら」 is mostly self-directed musing or a soft query that does not press for an answer, has a feminine feel, and is limited to speech; 「か」 addresses someone directly, and 「ですか」 works in formal settings. With negative forms, 「かしら」 can also express hope or request.
• でしょうN5Use 「か」 when you don't know the answer and ask the other person; 「でしょう」 expresses conjecture—said with rising intonation, it means you already have your own judgment and seek agreement, so the two are not interchangeable. For example, 「雨ですか」 is a question, while 「雨でしょう？」 seeks confirmation. They can combine as 「でしょうか」 for a gentler question.

か is the basic question marker, while か〜か lists alternatives or uncertain options, かどうか embeds a yes/no question ('whether or not'), and それとも is a conjunction meaning 'or' between two questions. かい is a casual, softer question ending, かしら expresses wondering ('I wonder'), and でしょう expresses conjecture rather than a direct question.