なにか / なにも

なんか何か is "something", or "anything" in a question. なん何も with a negative is "nothing", "not anything". Both take the place of the noun in the sentence, and が and を usually drop after them.

何か or 何を

なん何を asks "what?" and wants a thing as the answer. 何か asks "anything?" and the answer is yes or no.

何も needs a negative

何も only works with a negative at the end of the sentence: ない, きごう〜ません, きごう〜なかった. Without one, the sentence is not Japanese. を and が disappear into も.

• × 何もします → 何もしません
• × 何もを食べない → 何も食べない

Other particles stay and come before も: なんに何にもきょうみ興味がない, "I'm not interested in anything".

Usage notes

These go beyond "something" and "nothing".

何か before a noun

Straight before a noun, 何か means "some kind of" or "any".

何かを

を can stay after 何か. It makes "something" sound a little more definite.