"I do not study."
Translation:저는 공부하지 않습니다.
To negate a verb or an adjective there are two forms of negation, short form negation (안) and long form negation (지 않다). 안 is a contraction of "no" / 아니. This explanation does not discuss negation with 못 (can not) which can also be used in long and short form negation.
Short form negation: 안 + inflected verb
안 가요 (do not go)
안 배워요 (do not learn)
안 마셔요 (do not drink)
Verbs and adjectives that already have a corresponding negation can not be used with short form negation. Example: 모르다 (to not know).
If the verb is a compound verb, then the short form negation will change. Compound verbs are of the form "noun + 하다". Recall that 하다 is the uninflected verb "to do".
Short form negation with compound verb: noun + 안 + 하다 inflected
키스 안 해요 (do not kiss)
수영 안 해요 (do not swim)
공부 안 해요 (do not study)
Long form negation: stem + 지 않다 inflected
먹지 않아요 (do not eat)
마시지 않아요 (do not drink)
비싸지 않아요 (is not expensive)
공부하지 않아요 (do not study)
Note that long form negation does not change when used with a compound verb.
So when does one use short form or long form negation?
Quoted from Basic Korean (Andrew Sangpil Byon):
"There is no meaning difference between the long form negation and the short form negation. Consequently they are used interchangeably. However, the long form negation tends to be more often used in written and formal communication."
Unit 18 of the aforementioned book exhaustively discusses negation in Korean language.
It probably marked it correct because the omission of the object particle 을 / 를 is acceptable in Korean language, though more informal. You placed a space between 공부 and 합니다. The following statement is grammatically correct: 저는 공부를 안 합니다
It's not correct to write 저는 안 공부합니다. 공부하다 is a compound verb. In compound negation with 안, the inflection of 하다 is placed after 안 as in 저는 공부 안 합니다.
The construction verb + 지 말다 is not related to formality.
verb stem + 지 말다 simply is a negated imperative or propositive
recall that 말다 is irregular in the imperative, so ㄹ is removed
So, “ 공부하지마” means “do not study” as an imperative
“저는 공부하지마” would not makes sense in this case.
Well, as was stated in the answer, there is a more thorough explanation in the previous answer by the user, which I assume is the top answer on this thread. I upvoted it; it does not deserve its downvote, as it is both factual, to the point, and refers to a more thorough explanation from earlier.
습니다 is a sentence ending for declarative sentences in the deferential speech level, when the predicate used ends in a consonant. When the predicate used ends in a vowel, then the ending becomes ㅂ니다, where ㅂ becomes the final consonant of the predicate stem.
My answer will probably not seem useful if you don't understand sentence endings and how they attach to predicates. I have a website that explains that here if you're interested: https://seoullatte.com/deferential-speech
Please read my entire answer above as it will explain everything. In brief:
- predicate stem + 지 않다 is a negated predicate.
- predicate stem + 습니다 or ㅂ니다 is not negated and in the deferential speech level
You can read more about the deferential speech level and negation here in a website I maintain: