알다 vs 모르다: Knowing vs Not Knowing

알다 (al-da, alda) · 모르다 (mo-reu-da, moreuda)

'알다' refers to the state of knowing or understanding something, while '모르다' means not having the information or not understanding it.

Comparison of Korean words 알다 and 모르다 meaning know and not know

Word-by-word breakdown

One lane per word — no nested boxes, just the gist.

알다(al-da, alda)

To know or understand something

When to use

knowing facts, understanding methods, recognizing people

The nuance

'알다' is used when someone is aware of or understands information or facts. It expresses a positive knowledge state and is used when the subject knows a fact or method.

모르다(mo-reu-da, moreuda)

To not know or not understand information or facts

When to use

lack of information, failure to understand, not recognizing people

The nuance

'모르다' is used when someone lacks information or does not understand something. It expresses a negative knowledge state and is used when the subject does not know a fact or method.

Real-world examples

  • 나는 그 사실을 알아.

    na-neun geu sa-sil-eul al-a., na neun geu sa sil eul al a.

    This sentence naturally expresses that the subject knows a fact.

  • 나는 그 사실을 몰라.

    na-neun geu sa-sil-eul mol-ra., na neun geu sa sil eul mol ra.

    This sentence naturally expresses that the subject does not know a fact.

  • 나는 그 방법을 모르다.

    na-neun geu bang-beop-eul mo-reu-da., na neun geu bang beop eul mo reu da.

    '모르다' as a verb must be conjugated with '-아/어', so using '모르다' alone is grammatically incorrect. The correct form is '모른다'.

  • 그 사람을 알아요?

    geu sa-ram-eul al-a-yo?, geu sa ram eul al a yo?

    This is a natural expression using '알다' to indicate recognizing a person.

  • 그 사람을 몰라요?

    geu sa-ram-eul mol-ra-yo?, geu sa ram eul mol ra yo?

    This is a natural expression using '모르다' to indicate not recognizing a person.

  • 나는 이 문제를 모르다.

    na-neun i mun-je-reul mo-reu-da., na neun i mun je reul mo reu da.

    Incorrect verb conjugation; '모른다' is the correct form.

  • 나는 그 사실을 알지 못해.

    na-neun geu sa-sil-eul al-ji mos-hae., na neun geu sa sil eul al ji mos hae.

    A natural sentence using the negative form of '알다' as '모르다'.

  • 나는 그 사실을 모른다.

    na-neun geu sa-sil-eul mo-reun-da., na neun geu sa sil eul mo reun da.

    This sentence accurately expresses that the subject does not know the fact.

Quick quiz

  1. Which sentence correctly uses '알다'?

    다음 중 '알다'를 올바르게 사용한 문장은?(da-eumjung'al-da'reulol-ba-reu-gesa-yong-hanmun-jang-eun?, daeumjung'alda'reulolbareugesayonghanmunjangeun?)
  2. Which sentence correctly uses '모르다'?

    다음 중 '모르다'를 올바르게 사용한 문장은?(da-eumjung'mo-reu-da'reulol-ba-reu-gesa-yong-hanmun-jang-eun?, daeumjung'moreuda'reulolbareugesayonghanmunjangeun?)
  3. Which word fits in '그 사람을 ___?'

    '그 사람을 ___?'에 들어갈 알맞은 단어는?('geusa-ram-eul___?'edeul-eo-galal-maj-eundan-eo-neun?, 'geusarameul___?'edeuleogalalmajeundaneoneun?)

What does it mean?

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