also: なんか
Is there something to eat?
Please contact me if anything happens.
Adverbial use expressing that something is felt or perceived in an unclear way. Often used with ～となく or ～知らず.
I thought something was off.
I don't know why, but it went well.
what (do you mean)?; so what?
Only with reading なにか
Interjection used to question someone's vague or evasive statement. Restricted to the reading なにか.
"Hey..." "What?"
Would you like to eat something?
Today I feel somehow lonely.
Is there something to drink?
Is there some kind of problem?
May I help you with something?
何か is used for an unspecified thing in general, while どれか implies choosing one unspecified item from a known set of options.
何か simply means 'something' or 'what', while 何なのか probes for the deeper meaning or true identity of something.
何か is the everyday word for 'something/some', while 何らか is a more formal, often written equivalent used mainly as 何らかの or adverbially.
何か is the common, neutral word for 'something' usable in any register, while 何やら is more literary and adds a nuance of vagueness or indirectness.
何か means 'something' in a specific instance, while 何事 with も or でも means 'everything/anything' in a broader, more sweeping sense.
何か means 'something' in affirmative or question contexts, while 何も is its negative counterpart meaning 'nothing at all'.
何か simply means 'something' in a straightforward way, whereas 何とか adds vagueness or a sense of 'or other' and can also mean 'somehow'.
何か means 'something' in affirmative sentences, while 何も requires a negative verb and means 'nothing'.
何か means 'something' (one unspecified thing), while 何でも means 'anything at all' (no restriction on which thing).