I am learning Korean and am practicing verb conjugation.

I decided to write "I study a book".

Following the conjugation for "하다" verbs, i wrote:

나는 책을 공부해.

But when i checked a translation for "i study a book", it said:

나는 책을 공부한다.

I am confused about why there's a ㄴ with the 하, and why 다 is added at the end?

  • 1
    pretty sure you mean "study" as in 공부한다 - mind if i edit your question before i answer it? Jan 11, 2018 at 20:15
  • 1
    I have personally experienced that men are more likely to sound gruff and say "내가 한다" - I'm doing it - whereas it seems like females use 해체 and sound more smooth and light "내가 해" - I'm doing it - but that's pure opinion - I asked two natives and one agreed and the other didn't ㅎㅎㅎ Jan 11, 2018 at 23:48
  • Koreans don't use the term 공부하다 for the way you used "studying".... They use 살피다(search) or 연구하다(research) etc.
    – Lemon
    Jan 14, 2018 at 2:23
  • 나는 책을 공부한다. is technically correct, but is something you you would use if you were writing an article, not in a normal face to face conversation. 나는 책을 공부해., 나는 책을 공부해요., 나는 책을 공부합니다 are all fine.
    – user17915
    Jan 15, 2018 at 3:49

2 Answers 2


Korean has lots of different speech levels, as described in this Wikipedia page.

When you said

나는 책을 공부해.

That's fine - it's the kind of thing you could say to a friend. That was using the 'Hae-che' (해체) style.

The translation you found...

나는 책을 공부한다.

Is also fine, but using the 'Haera-che' (해라체) style. As described in the wiki page, you often see it in books, but it's perhaps not one of the most common styles used when actually talking to people - at least for action verbs.

WEBjuju's answer has a good description of the difference between action and descriptive verbs in this style; From my experience, using descriptive verbs in the 'Haera-che' style is more common than using action verbs in this style.


I'm pretty sure you mean

공부한다 to study

so the "dictionary form" is 공부하다. from there it can be conjugated many many different ways, but let me focus a minute just on why the ㄴ다 was added.

Verbs are broken down into two main categories, as shown by the headers below.

Action Verbs

The main conjugation into an informal, lacking polite form version adds ㄴ or 는 depending if the final sound is a vowel or not. Like this:

Dictionary form (minus 다) + ㄴ/는다

In the case of 공부하 + we must use the ㄴ by itself. If you were to conjugate the dictionary form of "to eat", the final sound is a consonant, so 는 is used instead.

먹다 (dictionary form) = 먹는다

Descriptive Verbs

The main conjugation of a descriptive verb into an informal, lacking polite form version adds...nothing. Like this:

Dictionary form

So in the case of 예쁘다 - it can just be used as is, straight out of the dictionary:

예쁘다 (dictionary form) = 예쁘다

Other conjugation examples of polite forms include:

공부하다 (dictionary form)

  • 공부하세요? Are you studying? (Do you study?)
  • 공부해요. I'm studying. (I study.)
  • 공부하십니까? Are you studying? (Do you study?)
  • 공부합니다. I'm studying. (I study.)


  • 예뻐요? Is it pretty? (Am I pretty? Is she pretty? etc)
  • 예뻐요. It is/she is/he is/I am/you are pretty.
  • 예쁩니까? Is it pretty? (Am I pretty? Is she pretty? etc)
  • 예쁩니다. It is/she is/he is/I am/you are pretty.

In conclusion

나는 책을 공부한다

is grammatically correct (and maybe more natural) and

나는 책을 공부해

is grammatically correct (but probably needs the 요 to be natural...depending on context and emotion).

Also...you can study the book, but "read" the book will trump the study in a frequency contest:

나는 책을 읽는다 (읽다 dictionary form of "to read").

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