Interrogatives I: 누구 (who), 무엇 / 뭐 (what) — and wh-in-situ

Two little words unlock most Korean questions about people and things: 누구 ("who") and 무엇 / 뭐 ("what"). But learning them is only half the job. The other half — the part that makes your questions actually sound Korean instead of translated — is a structural fact English hides from you: Korean leaves its question words exactly where the answer would go. English yanks "what" and "who" to the front of the sentence; Korean does not move them an inch. Get that word-order instinct right early, and a whole category of stilted, English-shaped questions never forms.

누구: "who"

누구 is the pronoun "who." It slots into the sentence like any noun and takes particles — with one famous irregularity in the subject form.

누구 with the other particles

Beyond subject and object, 누구 stacks with the dative and "with" particles just like any person noun — and this is where English's one-size-fits-all "who" really shows its poverty. English uses the bare word "who" for to whom, with whom, and because of whom; Korean marks each role explicitly on 누구:

• 누구한테 / 누구에게 — to whom (dative)
• 누구랑 / 누구하고 / 누구와 — with whom
• 누구 때문에 — because of whom

Because the particle carries the role, you can't get away with a bare 누구 the way English gets away with "who" — the listener needs to know whether you mean the caller, the called, or the companion. Pick the particle that matches the verb's frame.

무엇 / 뭐: "what"

"What" comes in two shapes. 무엇 is the full form — you'll see it in writing, formal speech, and service language. In everyday conversation it collapses to 뭐, which is what you'll say and hear the vast majority of the time.

Notice the register split in action: 무엇을 도와드릴까요? is what a hotel clerk says; with a friend you'd say 뭐 도와줄까? The meaning is identical — only the formality changes.

The headline: Korean is wh-in-situ

Here is the structural fact that reshapes your questions. English is a wh-fronting language: to ask about the object of "eat," you rip the question word out of its slot and haul it to the front — "What did you eat _?" — and you add a helper verb, "did." Korean does neither. It is wh-in-situ ("in place"): the question word sits in the very slot where the answer will appear, and the sentence's SOV order is left completely undisturbed.

Compare the question and its answer — the question word and the answer occupy the same position:

• 뭐 먹어요? → 김밥 먹어요. ("What are you eating?" → "I'm eating gimbap.")
• 누가 왔어요? → 민수가 왔어요. ("Who came?" → "Minsu came.")

There is no inversion and no do-support. A question is signaled instead by the sentence-final ending plus rising intonation. In 해요체, statement and question look identical on paper — 뭐 먹어요 is both "you're eating something" and "what are you eating?" — and intonation carries the difference. (In the formal 합니다체, the ending itself changes: 먹습니다 → 먹습니까?)

This is why forcing English structure produces broken Korean: there's no slot at the front for the question word, and no "do" to borrow. You simply drop 뭐 or 누구 into the answer's place and let the ending do the asking.

The in-situ design has an elegant payoff: because nothing moves, Korean can hold two question words in one clause with no strain. English struggles here — "who ate what?" is already awkward, and "who bought what for whom?" barely parses — but Korean just leaves each wh-word in its own slot:

Each word sits where its answer will go (누가 → the person, 뭐 → the dish), and the sentence stays perfectly natural. Fronting would make this impossible; keeping everything in place makes it trivial.

A preview: these same words mean "someone / something"

One more thing to file away. 누구 and 뭐 lead a double life: with the right intonation and endings they become indefinites — 누구 = "someone," 뭐 = "something." "누구 왔어요?" with falling-then-rising intonation can mean "did someone come?" rather than "who came?" This ambiguity is systematic and gets its own treatment in Question words as indefinites. For now, just know the words aren't locked to their interrogative meaning.

Common Mistakes

1. ×누구가 for the subject. The subject of 누구 is the irregular fused form 누가. This is probably the most common single error with 누구.

2. Marking "what (the object you're eating)" with the subject particle. 뭐 먹어요 means "what are you eating." Add 가 and you flip it: 뭐가 먹어요 asks "what is eating (something)?" The object of eating is bare 뭐 or 뭘, never 뭐가.

3. Fronting the question word English-style, or hunting for a "do." Korean has no fronting and no do-support. Keep normal order; let intonation and the ending ask.

4. Putting 누가 in an object slot. The 누가 fusion is subject-only. For "who(m)" as an object, it's the regular 누구를.

5. Using 무엇 in casual chat. 무엇 is the written/formal form. Dropping it into a friendly conversation sounds like a news anchor. Use 뭐.

Key Takeaways

• 누구 = "who," with the irregular subject 누가 (never ×누구가); object 누구를, possessive 누구.
• 무엇 / 뭐 = "what" — 무엇 in writing/formal speech, 뭐 in everyday conversation (object 뭘).
• Korean is wh-in-situ: the question word stays in its normal SOV slot, with no fronting and no do-support. Rising intonation plus the final ending makes the question.
• 뭐 (bare) is the object of "eat"; 뭐가 would make "what" the subject — a meaning flip.
• 누구 and 뭐 also serve as indefinites ("someone / something"), covered on the next pages.