Korean verbs look intimidating in a dictionary — 가다, 먹다, 마시다, 공부하다 — and then change shape completely in a sentence: 가요, 먹어요, 마셔요, 공부해요.
There is one rule behind all of it, and it comes down to a single vowel.
Step 1: Find the stem
Every Korean verb in the dictionary ends in 다. Remove it and you have the stem.
| Dictionary form | Stem |
|---|---|
| 가다 | 가 |
| 먹다 | 먹 |
| 마시다 | 마시 |
| 읽다 | 읽 |
| 하다 | 하 |
The stem never appears alone. It is a building block that endings attach to.
Step 2: Look at the last vowel of the stem
This is the whole rule.
If the last vowel is ㅏ or ㅗ → add 아요
- 가 + 아요 → 가요
- 앉 + 아요 → 앉아요
- 좋 + 아요 → 좋아요
Anything else → add 어요
- 먹 + 어요 → 먹어요
- 읽 + 어요 → 읽어요
- 마시 + 어요 → 마셔요
하다 verbs → 해요
- 하 → 해요
- 공부하 → 공부해요
- 일하 → 일해요
하다 is irregular but so common that you learn it as its own case rather than as an exception.
Step 3: The contractions
This is where the rule seems to break, and it does not — the vowels just merge.
| Stem | Expected | Actual |
|---|---|---|
| 가 | 가아요 | 가요 |
| 오 | 오아요 | 와요 |
| 보 | 보아요 | 봐요 |
| 주 | 주어요 | 줘요 |
| 마시 | 마시어요 | 마셔요 |
| 배우 | 배우어요 | 배워요 |
| 되 | 되어요 | 돼요 |
The pattern:
- ㅏ + 아 → just ㅏ (가아 → 가)
- ㅗ + 아 → ㅘ (오아 → 와)
- ㅜ + 어 → ㅝ (주어 → 줘)
- ㅣ + 어 → ㅕ (마시어 → 마셔)
You do not have to memorise these as separate items. Say the two vowels quickly and they merge on their own — the spelling just records what your mouth already does.
The verb 이다
이다 (to be) does not follow the pattern. It attaches directly to a noun and changes shape based on whether the noun ends in a consonant.
- 학생 + 이에요 → 학생이에요 (I'm a student)
- 의사 + 예요 → 의사예요 (I'm a doctor)
Consonant ending takes 이에요, vowel ending takes 예요.
Why this rule is worth memorising properly
Because 아요/어요 is not one ending. It is a form that dozens of other endings attach to.
Once you know 먹어요, you get these almost for free:
| Form | Meaning |
|---|---|
| 먹었어요 | ate (past tense) |
| 먹어서 | because I ate |
| 먹어 주세요 | please eat |
| 먹어 봤어요 | I've tried eating |
| 먹어도 돼요 | you may eat |
All of them are built on 먹어. Learn the rule once and a large amount of grammar downstream stops requiring separate memorisation.
Making it negative
Two ways, both easy.
안 + verb — the short one, most common in speech.
- 안 가요. — I don't go.
- 안 먹어요. — I don't eat.
For 하다 verbs, 안 goes between the noun and 하다: 공부 안 해요.
Stem + 지 않아요 — slightly more formal.
- 가지 않아요.
- 먹지 않아요.
The mistakes to watch for
Applying the rule to the wrong vowel. It is the last vowel of the stem, not of the dictionary form. 마시다 has ㅣ as its last stem vowel, so 마셔요.
Forgetting 하다 verbs. Any verb ending in 하다 becomes 해요, regardless of what comes before it.
Writing out the uncontracted form. 가아요 and 보아요 are not wrong exactly, but they are not what anyone says or writes.
How it becomes automatic
Not through conjugation tables. Through hearing verbs in sentences until the correct form is what comes to mind first.
K-PATTO episodes are short dialogues, which means the same common verbs appear in their conjugated forms constantly — 가요, 먹어요, 해요, 있어요 — in context, with audio. The first ten episodes are free at K-PATTO.