Connecting Reason and Result
When you want to explain why something happened, you can connect two short sentences into one smooth sentence using the connector -아서/-어서 .
The first part of the sentence becomes the reason , and the second part is the result or action.
Structure
Reason
Connector
Result
비가 오다
-아서
집에 있어요
Choosing the Right Form
You choose between -아서 , -어서 , and -해서 based on the last vowel of the predicate stem. If you know how to conjugate basic present tense verbs, you already know how to do this!
The Basic Rule
-아서 : If the last vowel is ㅏ or ㅗ (오다 → 와서)
-어서 : If the last vowel is anything else (없다 → 없어서)
-해서 : For all verbs ending in 하다 (피곤하다 → 피곤해서)
Combining Sentences in Practice
Let's look at how two ideas connect naturally. Notice how the first sentence explains the reason for the second.
비가 와요.
집에 있어요.
→
비가 와서 집에 있어요.
It is raining, so I am at home.
시간이 없어요.
택시를 탔어요.
→
시간이 없어서 택시를 탔어요.
I didn't have time, so I took a taxi.
Important Rule: Tense Only at the End
A very common mistake is putting a past tense marker in the middle of the sentence before the connector.
When using -아서/-어서 , the first part of the sentence (the reason) does not take a tense marker. You only show the tense at the very end of the completed sentence.
Common Mistake