In short

To ask a question in Korean you change almost nothing: keep the sentence exactly as it is and drop the question word into the slot where the answer would go. 이게 뭐예요? (Ige mwoyeyo?) “What is this?” has the same shape as the statement that answers it. For yes/no questions in 해요체 you change nothing at all - you just raise your voice at the end.

The rule

Step 1 - The question word sits in the answer’s slot

English moves question words to the front: “You are eating what?” becomes “What are you eating?” Korean does no such thing. The sentence keeps its normal verb-final order and the question word simply occupies the position of the missing information.

• 어디 가요? (Eodi gayo?) - Where are you going? -> answer 학교 가요. (Hakgyo gayo.) I’m going to school.
• 어디 stands exactly where 학교 stands. Nothing moved.

So the procedure for building any question word question is: write the answer, then swap the unknown part for a question word. That single habit removes most beginner word-order errors.

Step 2 - Yes/no questions are intonation only

In 해요체 the statement and the yes/no question are the same words with the same ending. Only the pitch differs - falling for a statement, rising for a question - and in writing only the question mark differs.

• 커피 좋아해요. (Keopi joahaeyo.) - You like coffee.
• 커피 좋아해요? (Keopi joahaeyo?) - Do you like coffee?

There is no Korean equivalent of “do”-support, no auxiliary, no inversion. (The formal question ending -습니까? exists, but it belongs to 합쇼체 and arrives at The formal deferential style 합쇼체. Do not mix it into 해요체 sentences.)

Step 3 - Answering: 네 and 아니요

네 (ne) is “yes” and 아니요 (aniyo) is “no”, but 네 is better understood as “that’s right” - it agrees with the proposition you were just handed rather than with the English polarity. 네 also works as “I’m listening”, “here you go” and “pardon?”, which is why you hear it constantly.

Step 4 - Question words take 이/가, never 은/는

An unknown thing cannot be your topic - you cannot announce “as for what…” So a question word in subject position must carry the subject particle 이/가, and the answer that fills the gap carries it too:

• 누가 왔어요? (Nuga wasseoyo?) - Who came? -> 제가 왔어요. (Jega wasseoyo.) I did.

Note the fusion: 누구 + 가 -> 누가, not *누구가. Learn 누가 as its own word, the subject form of 누구. The same applies to 뭐: 뭐가 좋아요? (Mwoga joayo?) Which one is good?

Answering 저는 왔어요 here would be wrong - 은/는 announces a topic, but the questioner asked for brand-new information, so 제가 is the only correct answer.

Step 5 - Some question words need a noun after them

무슨, 어느 and 어떤 are determiners: they modify a following noun and cannot stand alone. They are spaced from that noun.

• 무슨 + Noun - what / what kind of, out of an open field.
• 어느 + Noun - which one, out of a known set.
• 어떤 + Noun - what sort of, what is it like.

몇 (myeot) is the same kind of word: it needs a counter after it - 몇 시 (myeot si) “what time”, 몇 개 (myeot gae) “how many items” - and is always spaced. Contrast 얼마 (eolma), which stands alone and asks price or quantity. Full coverage of counters is in Two number systems, counters, time and dates; the determiner family is mapped in Demonstratives 이/그/저 and place words.

Step 6 - The same words also mean “someone / something / sometime”

Korean question words are indefinite pronouns too. The words do not change; the intonation does, and so does the particle.

• 누구 있어요? (Nugu isseoyo?) - Is anyone there? (not “who is there?”)
• 뭐 좀 먹었어요? (Mwo jom meogeosseoyo?) - Did you eat something?
• 어디 갔어요? (Eodi gasseoyo?) - with the stress on 어디 this is where did you go?, but said flatly it is did you go somewhere?

The tell is the particle: a real question word in subject position takes 이/가 (누가 있어요? Who is there?), while the indefinite reading leaves it bare or takes 은/는.

Forms & patterns

The core inventory. These ten cover almost everything you need at A1:

How 누구 and 뭐 behave with particles. Both end in a vowel, so they select the vowel-side allomorph every time:

The determiners - each one needs a noun, spaced:

Answering yes and no:

Examples

Common mistakes

• 누구가 왔어요? (Nuguga wasseoyo?) -> 누가 왔어요? (Nuga wasseoyo?) - 누구 plus the subject particle fuses into the single word 누가. The uncontracted form does not exist.
• 누가 왔어요? - 저는 왔어요. (Jeoneun wasseoyo.) -> 제가 왔어요. (Jega wasseoyo.) - the answer to a 누가 question is the new information the questioner asked for, so it takes 이/가. 은/는 would announce a topic instead of answering.
• 뭐는 맛있어요? (Mwoneun masisseoyo?) -> 뭐가 맛있어요? (Mwoga masisseoyo?) - question words cannot carry 은/는 at all. You cannot make an unknown into the thing you are talking about.
• 뭐해요? (Mwohaeyo?) -> 뭐 해요? (Mwo haeyo?) - 뭐 is an independent pronoun, not a prefix, so it is spaced from the verb. Compare 공부해요, which really is one word.
• 어떻게 사람이에요? (Eotteoke saramieyo?) -> 어떤 사람이에요? (Eotteon saramieyo?) - 어떻게 is an adverb (“by what means”) and attaches to a verb. In front of a noun you need the determiner 어떤.

Tips

• Write the answer first, then swap. Because nothing moves, you can build any question by writing the full statement and replacing the unknown word. This is the fastest way to stop producing English word order in Korean.
• 네 agrees, it does not mean “yes”. If someone asks a negative question - “you’re not going?” - Korean 네 means that’s right, I’m not going, exactly where English would say “no”. Answer the proposition, not the polarity.
• 얼마 asks an amount, and money is only its commonest one. 얼마 stands alone before the copula (얼마예요?) and equally bare in front of a verb, with its particle dropped (얼마 올랐어요? how much has it gone up?); 몇 is a determiner and must be glued to a counter with a space (몇 시, 몇 개, 몇 사람). Writing *몇시 is a spacing error.
• 뭐 and 무엇 are the same word in two registers. Say 뭐 in conversation and write 무엇 in formal or written Korean. A learner who says 무엇이에요 out loud sounds like a textbook; a learner who writes 뭐 in an exam essay sounds too casual. They do not take the same particles, though: 무엇 ends in the 받침 ㅅ, so it takes the consonant side - 무엇이, 무엇을, 무엇이에요 - where 뭐 takes 뭐가, 뭐를, 뭐예요.