Translation guide
The English word 'whether' is used to introduce indirect questions or express alternatives. In Japanese, it is most commonly expressed using the particle か (ka) or the phrase かどうか (ka dou ka). The choice depends on whether the embedded question is a yes/no question or an open-ended question, and on the level of formality.
I don't know whether he will come or not.
Alternative pattern: verb + か + negative verb + か.
Expressing uncertainty about a yes/no proposition, equivalent to 'whether or not'.
Attach to the plain form of a verb, adjective, or noun + だ to embed a yes/no question. This is the most common and neutral way to say 'whether or not'.
Do you know whether he will come?
I don't know whether that's true.
I want to try whether this dish is delicious.
Simply use the question particle か after a plain form clause. This is more common in formal or written contexts, and can sometimes sound abrupt in casual speech. Often used with verbs like 分かる, 知る, 決める.
Please tell me when the meeting starts. (lit. whether the meeting starts when)
Repeat the verb/adjective in positive and negative forms to emphasize the alternatives. More explicit than かどうか.
I don't know whether he will come or not.
A formal, literary equivalent of かどうか. Used primarily in written language or formal speeches.
Embedding a question with a question word (who, what, where, etc.) to express 'whether' in the sense of 'I don't know who/what/where...'.
Use the question word (だれ, なに, どこ, etc.) followed by the plain form of the predicate and か. This is the standard way to embed open-ended questions.
I don't know who will come. (lit. I don't know whether who will come.)
Expressing a choice between two or more alternatives, often with 'or'.
List the alternatives with か between them. The final か is often followed by a verb like 分からない, 決める, etc.
Expressing 'no matter whether' or 'regardless of whether', often with a concessive meaning.
Formal pattern meaning 'regardless of whether or not'. Used in written and formal spoken Japanese.
Using 'whether' to introduce a clause that acts as the subject of a sentence, often with 'or not'.
Nominalize the embedded question with かどうか and mark it as the subject with が.
Use かどうか when the embedded question is a yes/no question (i.e., 'whether or not'). Use か alone when the embedded question contains a question word (who, what, where, etc.) or when listing alternatives. In casual speech, かどうか can be shortened to か, but this can be ambiguous.
I don't know whether he'll come or not.
I wonder whether it will rain tomorrow.
彼が来るか分からない。
I don't know whether he'll come.
それが正しいか正しくないか判断できない。
I can't judge whether that is correct or not.
It is still unknown whether the bill will be passed or not.
Please decide what you want to eat.
I haven't decided where to go yet.
Rarely used, but possible when the question word is the subject of a yes/no proposition. For example, 'whether someone will come' can be rephrased as 'whether there is someone who will come'.
I don't know whether anyone will come.
Which would you like, coffee or tea? (lit. Whether coffee or tea, which is good?)
Decide quickly whether you're going or not.
Use それとも to explicitly mean 'or' when presenting two alternatives, especially in questions.
Please decide whether to go by train or by bus.
You can apply regardless of whether you have experience or not.
Similar to にかかわらず, but slightly less formal. Means 'regardless of whether'.
The event will be held regardless of whether the weather is good or not.
A formal, literary pattern meaning 'whether A or B'. Used with nouns or na-adjectives.
Whether it's rain or snow, the game will be held.
Whether he comes or not is the problem.
Whether that is true or not is not important.
Using は instead of が adds a contrastive or thematic nuance.
Whether he succeeds or not depends on his effort.
誰が来るか分からない。
I don't know who will come.
English often uses 'whether or not' for emphasis. In Japanese, かどうか already includes the 'or not' meaning. Adding かどうかかどうか or similar is incorrect. Use かどうか for neutral yes/no embedding, and か〜か for explicit alternatives.
I haven't decided whether to go or not.
In very casual conversation, かどうか is often shortened to just か, especially with verbs like 分かる. However, this can sometimes sound blunt. To soften, add かどうか or use 〜か〜か.
I dunno if he's coming.
It doesn't matter whether you agree or not.
She asked whether I had finished my homework.