pronoun
what; which things
Used when asking about or referring to multiple unspecified things, often in a list or when the speaker expects several items.
好きな食べ物は何々ですか。
What are your favorite foods? (expecting multiple answers)
必要な書類は何々か教えてください。
Please tell me what documents are needed.
pronoun
so-and-so; such and such; something or other
Used when listing things that are unknown or do not need to be specified, like 'so-and-so' or 'such and such' in English.
彼は何々が理由で遅れたと言っていた。
He said he was late because of such and such.
会議では何々の件について話し合った。
At the meeting, we discussed matters like so-and-so.
interjection
Interjection used when asking for confirmation upon hearing something surprising; expresses mild shock or disbelief.
何々？本当にそう言ったの？
What? Did he really say that?
interjection
well, well; let's see
Interjection used when about to read a letter or document, often with a tone of curiosity or mild surprise.
何々、手紙が来ている。何て書いてあるかな。
Well, well, a letter has arrived. Let's see what it says.
interjection
no; oh (not at all); please; there, there
Interjection used to dismiss someone's words or concerns, often in a reassuring or humble way; can sound old-fashioned.
何々、お気になさらずに。
Oh, please don't mention it.
Reduplication of 何 (なに, 'what'), used to indicate multiple unspecified things or as an interjection. The exact historical development is uncertain, but the form is well-established in modern Japanese.