When learning Korean, students often struggle with connecting sentences naturally. Two commonly used connective endings, -아서/어서/해서 and -고, often confuse learners. Both connect two actions or events, but their meanings and functions are different. This post will explain their differences in structure, meaning, and usage, with many real-life examples to help clarify.
Contents
1. What Are -아서/어서/해서 and -고?
-아서/어서/해서
-아서/어서/해서: This ending expresses sequential or causal relationships. It indicates that the first action leads to the second or that two actions happen in a closely related sequence.
-고
The connective 고 is used to simply list actions or describe sequential actions without indicating causality.
2. How to Form -아서/어서/해서 and -고
-아서/어서/해서 Conjugation Rules
| Verb Type | Conjugation Rule | Example |
| Verbs with ㅏ or ㅗ in the root | Add -아서 | 가다 → 가서 (to go → I went) |
| Verbs with other vowels | Add -어서 | 먹다 → 먹어서 (to eat → I ate) |
| 하다 Verbs | Add -해서 | 공부하다 → 공부해서 (to study → I studied) |
-고 Conjugation Rules
| Word Type | Conjugation Rule | Example |
| Verbs | Attach -고 to the verb stem | 먹다 → 먹고 (eat and) |
| Adjectives | Attach -고 to the adjective stem | 크다 → 크고 (is big and) |
3. When and How to Use -아서/어서/해서 vs. -고: Key Differences and Usage Tips
Key Differences Between -아서/어서/해서 and -고
While -아서/어서/해서 and -고 may seem similar, their usage and meaning can vary significantly based on context. Below are the main points to remember:
- -아서/어서/해서:
- Primarily used to indicate sequential actions or a cause-and-effect relationship.
- It shows one event happening after another, but it can also express causality.
- Examples:
- 나는 배가 고파서 밥을 먹었어요. (I was hungry, so I ate.)
- Cause → Effect: Being hungry is the cause, and eating is the effect.
- 친구를 만나서 영화를 봤어요. (I met my friend and watched a movie.)
- This sentence can show temporal sequence: I met my friend and then watched a movie. It does not always imply cause and effect.
- 비가 와서 우산을 썼어요. (It rained, so I used an umbrella.)
- Cause → Effect: It raining is the cause, and using an umbrella is the effect.
- Cause → Effect: It raining is the cause, and using an umbrella is the effect.
- 나는 배가 고파서 밥을 먹었어요. (I was hungry, so I ate.)
- Note : While -아서/어서/해서 often indicates a cause-and-effect relationship, it can also simply show actions happening in order, without causality.
- -고:
- Used to list actions in sequence or show simultaneous events.
- Unlike -아서/어서/해서, it can also be used when actions occur at the same time.
- Examples:
- 나는 아침에 일어나고 샤워를 해요. (I wake up in the morning and take a shower.)
- Sequential: Waking up happens first, then taking a shower happens second.
- 친구를 만나고 영화를 봤어요. (I met my friend and watched a movie.)
- Sequential: Meeting my friend happens first, then watching a movie happens second.
- 비가 오고 바람이 불어요. (It’s raining, and the wind is blowing.)
- Simultaneous: The rain and the wind are happening at the same time.
- 한국어를 배우고 영어를 가르쳐요. (I learn Korean and teach English.)
- Sequential: Learning Korean happens first, then teaching English happens second.
- Sequential: Learning Korean happens first, then teaching English happens second.
- 나는 아침에 일어나고 샤워를 해요. (I wake up in the morning and take a shower.)
- Note: One key difference between -고 and -아서/어서/해서 is that -고 can express simultaneous actions, while -아서/어서/해서 generally implies cause and effect or temporal sequence but not simultaneous events.
When to Choose -아서/어서/해서 and -고: How to Decide
Sometimes, -아서/어서/해서 and -고 can be used interchangeably, especially when the relationship between actions is neutral and not heavily based on cause-and-effect. For example:
- -아서/어서/해서: “친구를 만나서 영화를 봤어요.” (I met my friend and then watched a movie.)
- -고: “친구를 만나고 영화를 봤어요.” (I met my friend and watched a movie.)
In this case, both structures indicate the sequence of events, and the meaning is very similar. However, keep in mind that -아서/어서/해서 can sometimes imply a cause-and-effect relationship, whereas -고 simply lists events or shows simultaneity.
Common Confusions: Specific Examples
Learning to differentiate between these two structures can be tricky, especially when both seem to express a sequence of events. Here are some examples where learners often get confused:
- Incorrect: “친구를 만나고 영화를 봤어요.” ❌ (This might be understood as “I met my friend, and then watched a movie,” but with -고, it doesn’t imply a cause.)
- Correct: “친구를 만나서 영화를 봤어요.” ✅ (This indicates a clear sequence of events, and “만나서” can imply that meeting the friend led to watching a movie.)
Similarly, when expressing simultaneous actions, -고 is the correct choice:
- Correct: “비가 오고 바람이 불어요.” ✅ (The rain and wind happen at the same time.)
- Incorrect: “비가 와서 바람이 불어요.” ❌ (This could imply that the rain caused the wind to blow, which isn’t the intended meaning.)
Comparison Table: -아서/어서/해서 vs -고
| Grammar Structure | Usage | Example |
| -아서/어서/해서 | Sequential actions with a natural connection, cause-and-effect relationship | “배가 고파서 밥을 먹었어요.” (I was hungry, so I ate.) |
| -고 | Listing actions in sequence (neutral) or simultaneous events | “비가 오고 바람이 불어요.” (It is raining and the wind is blowing.) |
In summary, -아서/어서/해서 is mainly used for sequential actions or cause-and-effect relationships, though it can sometimes indicate a simple time sequence. On the other hand, -고 is more flexible, often used to list actions sequentially or to show simultaneous events. Understanding these differences and the specific contexts where these structures are used will help you use them correctly in everyday conversations.
4. Practice Exercises
Directions: Choose the correct connector (-아서/어서/해서 or -고) from the given options and fill in the blanks.
⚠ Note: All sentences below express actions happening in order (“and then”). Choose the correct connector based on whether the two actions are naturally connected (-아서/어서/해서) or just listed in order (-고).
- 감기가 심하게 (걸려서 / 걸리고) 병원에 갔어요.
(I caught a bad cold and then went to the hospital.) - 친구를 만나 (얘기해서 / 얘기하고) 저녁을 먹었어요.
(I met my friend and then had dinner.) - 아침에 일어나 (세수해서 / 세수하고) 이를 닦았어요.
(I woke up in the morning and then washed my face.) - 도서관에서 책을 빌려 (읽어서 / 읽고) 정리했어요.
(I borrowed a book from the library and then organized it.) - 버스를 타 (학교에 가서 / 학교에 가고) 수업을 들었어요.
(I took the bus and then went to school for class.) - 비가 (와서 / 오고) 나무가 젖었어요.
(It rained, and then the tree got wet.) - 숙제를 (끝내서 / 끝내고) 텔레비전을 봤어요.
(I finished my homework and then watched TV.) - 운동을 (하고 나서 / 하고) 샤워를 했어요.
(I exercised and then took a shower.) - 편지를 (써서 / 쓰고) 우체국에 보냈어요.
(I wrote a letter and then sent it at the post office.) - 여행을 (계획해서 / 계획하고) 항공권을 예매했어요.
(I planned my trip and then booked a flight ticket.)
5. Answers
⚠ Note: The correct answers follow the “and then” rule. This means the first action occurs before the second action, and they are linked in a natural order.
- 감기가 심하게 (걸려서 / 걸리고) 병원에 갔어요.
✅ 정답: 걸려서
💡 Why? “I caught a cold → then I went to the hospital.” (Cause and effect, this follows the “and then” rule with -아서/어서/해서.) - 친구를 만나 (얘기해서 / 얘기하고) 저녁을 먹었어요.
✅ 정답: 얘기하고
💡 Why? “I met my friend → then we had dinner.” (This is a sequence of two independent actions, so it works with -고.) - 아침에 일어나 (세수해서 / 세수하고) 이를 닦았어요.
✅ 정답: 세수하고
💡 Why? “I woke up → then washed my face and brushed my teeth.” (This is a natural sequence of actions, so -아서/어서/해서 fits.) - 도서관에서 책을 빌려 (읽어서 / 읽고) 정리했어요.
✅ 정답: 읽고
💡 Why? “I borrowed a book → then read and organized it.” (This is a sequence of actions, so -고 is correct.) - 버스를 타 (학교에 가서 / 학교에 가고) 수업을 들었어요.
✅ 정답: 학교에 가서
💡 Why? “I took the bus → then went to school for class.” (This is a clear sequence, so -아서/어서/해서 is correct.) - 비가 (와서 / 오고) 나무가 젖었어요.
✅ 정답: 와서
💡 Why? “It rained → so the tree got wet.” (Cause and effect, following the natural progression of -아서/어서/해서.) - 숙제를 (끝내서 / 끝내고) 텔레비전을 봤어요.
✅ 정답: 끝내고
💡 Why? “I finished my homework → then watched TV.” (Separate actions in sequence, so -아서/어서/해서 works.) - 운동을 (하고 나서 / 하고) 샤워를 했어요.
✅ 정답: 하고
💡 Why? “I exercised → then took a shower.” (This is a sequence of sequential actions, so -고 fits.) - 편지를 (써서 / 쓰고) 우체국에 보냈어요.
✅ 정답: 쓰고
💡 Why? “I wrote the letter → then sent it at the post office.” (Clear sequence, so -고 is correct.) - 여행을 (계획해서 / 계획하고) 항공권을 예매했어요.
✅ 정답: 계획하고
💡 Why? “I planned my trip → then booked a flight ticket.” (Separate actions in sequence, so -고 works.)
By understanding the key differences between -아서/어서/해서 and -고, you can use them naturally in your Korean conversations. Keep practicing with real-life examples to master their nuances!