Connecting Actions in Time
When you do one thing and then another, Korean typically connects the two actions using either -고 or -아서/-어서 .
The choice between them depends on how closely the first action relates to the second action. Instead of memorizing strict rules, look at the relationship between the two events.
Independent Actions with -고
Use -고 when you are simply listing actions in time order. The two actions are relatively independent.
아침을 먹어요.
학교에 가요.
These are two separate events that happen one after the other. We connect them with -고.
아침을 먹고 학교에 가요.
The action of eating breakfast does not directly cause or physically carry over into going to school. It is just a neutral sequence.
Tightly Linked Actions with -아서/-어서
Use -아서/-어서 when the first action is physically or logically linked to the second action. This usually happens when the location or the object from the first action carries over into the next.
친구를 만나요.
같이 점심을 먹어요.
You cannot eat lunch with the friend without meeting them first. The actions are tightly linked.
친구를 만나서 같이 점심을 먹어요.
Another common pattern is buying or making something, and then doing something with that object:
선물을 사서 친구에게 줘요. (I buy a gift and give it to a friend.)
Comparing -고 and -아서/-어서
Seeing the two connectors side by side helps clarify their different roles.
Connector · Example · Relationship
-고 · 밥을 먹고 공원에 가요. · Eating and going to the park are independent events in a timeline.
-아서/-어서 · 공원에 가서 산책해요. · Going to the park is the required location to take a walk.
Notice how going to the park is the second action in the first sentence, but the first action in the second sentence. The connector changes based on what happens next.