Something, someone
Question word + ka = some-, used to ask whether rather than what.
nanika
something; anything
何か なにか
Asks whether there is something (nanika atta?) or offers something unspecified (nanika nomu?); in fast speech it becomes nanka.
nanika atta no?
Did something happen?
何かあったの?
nanika atta n desu ka?
Did something happen?
何かあったんですか?
Casually most people say nanka: nanka atta no? The same nanka is also a filler (Responses, reactions, fillers & social phrases).
dareka
someone; anyone
誰か だれか
An unspecified person: dareka kita? asks whether anyone came, while dare ga kita? asks who came.
sakki dareka kita?
Did someone come by earlier?
さっき誰か来た?
sakki dareka kimashita ka?
Did someone come by earlier?
さっき誰か来ましたか?
dokoka
somewhere
どこか
An unspecified place, often with the particle after it dropped (dokoka iku?); doko iku? would ask where.
dokka iku no?
Are you going somewhere?
どっか行くの?
dokoka iku n desu ka?
Are you going somewhere?
どこか行くんですか?
Casually dokoka is said dokka (どっか #788); use dokoka in polite speech.
Learn alongside: nanika, dareka, itsukaLearn first: doko, nanika
itsuka
someday; sometime
いつか
An unspecified time, mostly for future wishes and loose plans (itsuka ikitai, itsuka mata).
itsuka ikitai na.
I'd love to go someday.
いつか行きたいな。
itsuka ikitai desu ne.
I'd love to go someday.
いつか行きたいですね。
itsuka also means 'the fifth (day)'; context separates them.
Learn alongside: nanika, dareka, dokokaLearn first: itsu, nanika