かどうかWhether or not, If...or not

Both か否か and かどうか express 'whether or not,' but differ in tone and usage. か否か is highly formal and mostly seen in legal documents, academic writing, or formal reports. かどうか is more common in daily conversation and general writing, making it the default choice in most situations.

かどうか expresses uncertainty, like 'whether or not', as in 行くかどうか分からない ('I don't know whether or not they'll go.'). ～ても～なくても presents two opposite possibilities and says the result is unchanged, like 降っても降らなくても行く ('Whether it rains or not, I'm going.').

Both can suggest contrastive options, but with different usage. かどうか focuses on 'whether or not' something is true. にしても～にしても means 'regardless of which', and is used for comparing two alternatives. For example, 楽しいにしてもつまらないにしても行く ('Whether it's fun or boring, I'll go.').

かどうか expresses uncertainty, as in 来るかどうか分からない ('I don't know whether or not they'll come.'). 〜でも〜でも lists multiple alternatives and suggests the outcome is unchanged. For example, 雨でも晴れでも行く ('Whether it rains or shines, I'll go.').

Both are embedded question forms. A question phrase plus か makes an indirect question, like 何時に来るか分からない ('I don't know what time they'll come'). かどうか focuses specifically on yes/no questions, like 来るかどうか分からない ('I don't know whether or not they'll come.').

Both express the sense of 'whether', but in different ways. かどうか is used to present uncertainty, as in 面白いかどうか分からない ('I don't know whether or not it's interesting.'). にしろ～にしろ expresses that something applies regardless of the case, like 面白いにしろつまらないにしろ観たい ('Whether it's interesting or boring, I want to watch.').

か何か and かどうか look similar but are used differently. か何か follows a noun and means 'or something,' as in お茶か何か飲みますか？ ('Would you like some tea or something?'). かどうか means 'whether or not' and expresses uncertainty, like 面白いかどうか分からない ('I don't know whether or not it's interesting.').

かどうか expresses binary uncertainty, like 'whether or not', as in 行くかどうか分からない ('I don't know whether or not they'll go.'). にしても adds a tone of concession or contrast, like 'even if'. For example, どこに行くにしても 'no matter where (you) go'. The former asks a yes/no-type question, the latter implies acceptance of a situation.