There is no higher-leverage verb pattern to learn in Korean than [noun] + 하다. Thousands of everyday verbs are built this way — 공부하다 (study), 사랑하다 (love), 시작하다 (begin), 일하다 (work), 전화하다 (phone), 운동하다 (exercise), 요리하다 (cook) — and every single one conjugates identically, because they all share the stem-final 하-. Learn the paradigm of 공부하다 ("to study," stem 공부하-) once and you have effectively conjugated an entire slice of the lexicon: chop off the noun, keep the 하- machine, swap in any other noun.
The one thing that makes 하다 special is a harmony exception. Where every other stem chooses between the vowels -아 and -어, 하- takes neither: it selects the archaic allomorph -여, and 하 + 여 always fuses to 해. So every 아/어-based cell in the grid below is built on 해 — 해요, 했어요, 해서 — never on ×하아 or ×하어. This is the fact to burn in first; see 하다 → 해: the 여-contraction for why.
The full paradigm
Rows are tense/mood; columns are the four speech levels — 합니다체 (formal-polite), 해요체 (informal-polite), 해체/반말 (intimate), and 한다체 (plain/written). Every cell shows the Hangul with its Revised Romanization.
| Tense / mood | 합니다체 (formal) | 해요체 (polite) | 해체 (intimate) | 한다체 (plain/written) |
|---|---|---|---|---|
| Present | 공부합니다 gongbuhamnida | 공부해요 gongbuhaeyo | 공부해 gongbuhae | 공부한다 gongbuhanda |
| Past | 공부했습니다 gongbuhaetseumnida | 공부했어요 gongbuhaesseoyo | 공부했어 gongbuhaesseo | 공부했다 gongbuhaetda |
| Future / intent (-겠) | 공부하겠습니다 gongbuhagetseumnida | 공부하겠어요 gongbuhagesseoyo | 공부하겠어 gongbuhagesseo | 공부하겠다 gongbuhagetda |
| Future (-ㄹ 거) | 공부할 겁니다 gongbuhal geomnida | 공부할 거예요 gongbuhal geoyeyo | 공부할 거야 gongbuhal geoya | 공부할 것이다 gongbuhal geosida |
| Negation — 안 (short) | 공부 안 합니다 gongbu an hamnida | 공부 안 해요 gongbu an haeyo | 공부 안 해 gongbu an hae | 공부 안 한다 gongbu an handa |
| Negation — 지 않다 (long) | 공부하지 않습니다 gongbuhaji anseumnida | 공부하지 않아요 gongbuhaji anayo | 공부하지 않아 gongbuhaji ana | 공부하지 않는다 gongbuhaji anneunda |
| Inability — 못 | 공부 못 합니다 gongbu mot hamnida | 공부 못 해요 gongbu mot haeyo | 공부 못 해 gongbu mot hae | 공부 못 한다 gongbu mot handa |
| Imperative | 공부하십시오 gongbuhasipsio | 공부하세요 gongbuhaseyo | 공부해 / 공부해라 gongbuhae / gongbuhaera | 공부해라 gongbuhaera |
| Propositive (let's) | 공부합시다 gongbuhapsida | 공부해요 gongbuhaeyo | 공부하자 gongbuhaja | 공부하자 gongbuhaja |
A few readings deserve a note. In 공부합니다 the ㅂ nasalizes to [m] before ㄴ, so it is said [공부함니다] (gongbuhamnida). The past 했 ends in ㅆ, which neutralizes to [t] before a consonant — hence 공부했습니다 → gongbuhaetseumnida, but 공부했어요 → gongbuhaesseoyo (the ㅆ liaises onto the following vowel). And 겠 before a consonant is romanized -get- (공부하겠습니다 → gongbuhagetseumnida), but -gess- before a vowel (공부하겠어요 → gongbuhagesseoyo).
The stem-based forms: connectives and modifiers
Connective endings and attributive (noun-modifying) endings do not vary by speech level — they attach to the same 하- stem no matter how polite the final verb is. Learn them once:
| Function | Form | Meaning |
|---|---|---|
| and (listing) | 공부하고 (gongbuhago) | studies and… |
| and so / because | 공부해서 (gongbuhaeseo) | study and then / because I study |
| if / when | 공부하면 (gongbuhamyeon) | if one studies |
| because (reason) | 공부하니까 (gongbuhanikka) | since I study |
| attributive — present | 공부하는 (gongbuhaneun) | (the person) who studies |
| attributive — past | 공부한 (gongbuhan) | who studied |
| attributive — prospective | 공부할 (gongbuhal) | who will study / to study |
| attributive — retrospective | 공부하던 (gongbuhadeon) | who used to study |
Notice 공부해서 is again the 여-contraction (해 + 서), while 공부하고, 공부하면, 공부하니까 attach to the bare 하- because those endings do not trigger the 아/어 slot. As an action verb, 공부하다 takes the present attributive -는 (공부하는 학생 "a student who studies"), which is where it differs from a descriptive verb like 좋다, whose present attributive is -은.
The forms in real sentences
The default polite register below is 해요체 — what you will actually speak most of the time.
요즘 도서관에서 한국어를 열심히 공부해요.
yojeum doseogwaneseo hangugeoreul yeolsimhi gongbuhaeyo
These days I study Korean hard at the library.
어제는 시험 때문에 밤새 공부했어요.
eojeneun siheom ttaemune bamsae gongbuhaesseoyo
Yesterday I studied all night because of the exam.
주말에는 보통 집에서 공부해.
jumareneun botong jibeseo gongbuhae
On weekends I usually study at home. (반말, to a friend)
저는 매일 회사에 다니면서 한국어를 공부합니다.
jeoneun maeil hoesa-e danimyeonseo hangugeoreul gongbuhamnida
I study Korean while going to work every day. (합니다체)
시험이 코앞인데 왜 공부 안 해요?
siheomi koapinde wae gongbu an haeyo?
The exam is right around the corner — why aren't you studying?
요즘 너무 바빠서 제대로 공부 못 했어요.
yojeum neomu bappaseo jedaero gongbu mot haesseoyo
I've been so busy lately that I couldn't study properly.
같이 도서관 가서 공부하자!
gachi doseogwan gaseo gongbuhaja!
Let's go to the library and study together! (propositive, 반말)
열심히 공부하는 학생일수록 질문이 많아요.
yeolsimhi gongbuhaneun haksaeng-ilsurok jilmuni manayo
The harder-studying a student is, the more questions they have. (present attributive 공부하는)
어릴 때 피아노를 배우던 기억이 나요.
eoril ttae pianoreul baeudeon gieogi nayo
I remember learning piano as a child. (retrospective -던)
The two classic traps
How this differs from English
English builds compound verbs too — do the studying, make a phone call, give a presentation — but it never fuses the noun and the light verb into one word, and it certainly does not run them through a single conjugation. Korean does. 공부하다 behaves as one lexical verb, so its tense, mood, and politeness all land on the 하- at the end, exactly where English would least expect the grammar to sit. The payoff is that the "irregular" 해 you memorize for one verb is not one verb's worth of work — it is the key to 사랑해요, 시작했어요, 전화할 거예요, 운동하자, and every other 하다-compound you will ever meet.
Common Mistakes
1. Applying vowel harmony to 하 (×하아요 / ×공부하아요). 하- never takes -아; it takes -여, which contracts to 해.
❌ 저는 매일 한국어를 공부하아요.
Wrong — 하 + 여 → 해; it is 공부해요, never ×공부하아요.
✅ 저는 매일 한국어를 공부해요.
jeoneun maeil hangugeoreul gongbuhaeyo
I study Korean every day.
2. Not splitting the noun under short negation (×안 공부해요). Short 안 goes between the noun and 해.
❌ 저는 요즘 안 공부해요.
Unnatural — short negation splits the noun: 공부 안 해요.
✅ 저는 요즘 공부 안 해요.
jeoneun yojeum gongbu an haeyo
I'm not studying much these days.
3. Regularizing the past to ×하았어요 / ×공부하았어요. The 해-contraction carries into the past: 했-.
❌ 어제 시험공부를 하았어요.
Wrong — the past of 하다 is 했어요; 시험공부를 했어요.
✅ 어제 시험공부를 했어요.
eoje siheomgongbureul haesseoyo
I studied for the exam yesterday.
4. Using -는다 where the plain form needs the fused 한다. The 한다체 present of a 하다-verb is 한다, not ×하는다.
❌ 그 학생은 매일 도서관에서 공부하는다.
Wrong — the plain present is 공부한다 (하 + ㄴ다), never ×공부하는다.
✅ 그 학생은 매일 도서관에서 공부한다.
geu haksaeng-eun maeil doseogwaneseo gongbuhanda
That student studies at the library every day. (한다체)
Key Takeaways
- 공부하다 = the template for thousands of verbs. Learn this grid; swap the noun (공부 → 사랑, 시작, 운동…) and the conjugation is identical.
- 하 + 여 → 해 in every 아/어 slot: present 공부해요, past 공부했어요, connective 공부해서 — never ×하아 / ×하어.
- Short negation splits the noun: 공부 안 해요 / 공부 못 해요, not ×안 공부해요. Long negation keeps it whole: 공부하지 않아요.
- 한다체 present is 한다 (not ×하는다); the present attributive is -는 (공부하는), because 하다 is an action verb.
- Connectives (하고, 해서, 하면, 하니까) and attributives (하는, 한, 할, 하던) are speech-level-invariant — they build on the same stem in every register.
Now practice Korean
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Start learning Korean→Related Topics
- 하다 (to do): Complete Paradigm, All Tenses × LevelsTOPIK 1 — The exhaustive reference grid for 하다 — the single highest-leverage verb in Korean, since thousands of noun+하다 verbs (공부하다, 사랑하다, 운동하다) inherit every one of its cells. Present, past, future, progressive, imperative, propositive, connectives, attributives, and nominal forms, all driven by one contraction: 하 + 여 → 해.
- 하다 → 해: The 여-ContractionTOPIK 1 — The one lexical exception to vowel harmony: 하다 takes neither -아 nor -어 but the archaic allomorph -여, and 하 + 여 always contracts to 해 — a single fixed output that conjugates thousands of 하다-compounds (공부해요, 사랑해, 시작해서).
- The Vowel-Contraction TableTOPIK 1 — The obligatory stem-vowel + 아/어 fusions that produce every 해요체 and past form — 가+아→가, 오+아→와, 주+어→줘, 마시+어→마셔 — plus the 되/돼 spelling test. The uncontracted forms are simply wrong.
- Negation Table: 안, 못, -지 않다, -지 못하다TOPIK 1 — Korean's four negation strategies laid out as SHORT (pre-verbal 안 / 못) vs LONG (-지 않다 / -지 못하다), with the split English merges: 안 = choosing not to, 못 = being unable to. Plus the three traps — 못 doesn't negate adjectives, 하다-verbs split under 안, and 'don't!' is -지 마세요, not 안.
- 먹다 (to eat): Consonant-Stem Verb ParadigmTOPIK 1 — The complete look-up paradigm of 먹다 across all four speech levels — the stencil for every regular consonant-stem action verb, with the obligatory 으 buffer that batchim stems insert before consonant-initial endings.