무엇 (mu-eos, mueos) · 뭐 (mwo)
'무엇' is used in formal or official contexts, while '뭐' is mainly used in casual, everyday conversations.
One lane per word — no nested boxes, just the gist.
'무엇' is an interrogative used in formal or polite contexts; it can be considered the full form of '뭐' and is precise and respectful.
When to use
formal questions, document writing, interview situations
The nuance
Use in formal writing, presentations, interviews, official documents, or any context requiring politeness and formality.
'뭐' is an informal interrogative commonly used in everyday conversation; it is a shortened form of '무엇' and sounds friendly and casual.
When to use
everyday conversation, talking with friends, informal situations
The nuance
Use in casual conversations with friends, family, colleagues, or informal situations.
무엇을 도와드릴까요?
mu-eos-eul do-wa-deu-ril-kka-yo?, mu eos eul do wa deu ril kka yo?
Appropriate as a formal and polite inquiry.
뭐 도와줄까?
mwo do-wa-jul-kka?, mwo do wa jul kka?
Natural and casual expression in friendly conversation.
무엇 하니?
mu-eos ha-ni?, mu eos ha ni?
'무엇' is formal and sounds awkward in casual talk; use '뭐 하니?' instead.
뭐를 찾으세요?
mwo-reul chaj-eu-se-yo?, mwo reul chaj eu se yo?
'뭐' does not combine with the object particle '를'; use '무엇을 찾으세요?'.
무엇이 필요합니까?
mu-eos-i pil-yo-hap-ni-kka?, mu eos i pil yo hap ni kka?
Appropriate formal expression for polite questioning.
뭐 필요해?
mwo pil-yo-hae?, mwo pil yo hae?
Natural, simple question in a casual context.
뭐가 필요합니까?
mwo-ga pil-yo-hap-ni-kka?, mwo ga pil yo hap ni kka?
Mixing informal '뭐' with formal ending '-습니까' is generally avoided.
무엇이 문제입니까?
mu-eos-i mun-je-ip-ni-kka?, mu eos i mun je ip ni kka?
Appropriate for asking about a problem in formal situations.
Which is used in formal situations?
Which is appropriate for casual talk with friends?
Which sentence is incorrect?
What does it mean?
