(Question-Phrase) + かIncluding questions within sentences

Both uses of か are extensions of its basic function as a question particle. When following a Wh-question word (like who, what, where, why, how), it creates a phrase meaning 'some-(word)' (e.g., 誰か = 'someone,' どこか = 'somewhere,' いつか = 'sometime'). When following regular nouns, it means 'or' (e.g., 今日か明日休みます = 'I'll take off today or tomorrow').

The なにか・なにも pattern combines the question word なに with particles to express ideas like 'something' or 'nothing.' This structure is based on how the particle か is used with question words within a sentence. For example, 何が食べたいか分かりますか？ means 'Do you know what (they) want to eat?'

The 誰か・どこか・誰も・どこも pattern combines question words like 誰 ('who') and どこ ('where') with particles to express ideas like 'someone' or 'somewhere.' These forms are also related to how the particle か is used with question phrases in embedded questions. For example, 誰が来るか分かりますか？ means 'Do you know who will come?'

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.').

Question-phrase + か embeds a question, e.g. 来るか分からない ('I don't know if they're coming.'). か〜ないかのうちに expresses something happening immediately at a moment of uncertainty, e.g. 来るか来ないかのうちに 'just as they arrived'.