Korean Cause and Result: Using -aseo/-eoseo for 'so' and -nikka for 'because'
Learn to connect Korean clauses with -aseo/-eoseo (so) and -nikka (because) to express cause and result, contrasting with -go (and), -jiman (but), and -geona (or).
By TheaFirst conversations · Yapr Learn
In Korean, connecting ideas goes beyond simple conjunctions like 'and' or 'but'. To express cause and result, you attach endings to verb stems. The ending -aseo/-eoseo means 'so' or 'because' and shows a natural result, while -nikka means 'because' and often gives a reason or justification. This lesson teaches you to form these connections accurately, so you can explain why something happened or what happened as a result. You will practice with everyday examples and learn to avoid common mistakes.
By the end, you can…
- use -aseo/-eoseo to say 'so' when one action naturally leads to another.
- use -nikka to give a reason or justify a statement.
- distinguish these cause-and-result endings from -go (and), -jiman (but), and -geona (or).
Listen once. Try it slowly. Then say it without looking.
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비가 와서 집에 있었어요.
It rained, so I stayed home.
bi-ga wa-seo ji-be i-sseo-sseo-yo.
Use -aseo after a verb stem ending in ㅏ or ㅗ (오다 → 와서). Shows a natural result.
배가 아파서 약을 먹었어요.
My stomach hurt, so I took medicine.
bae-ga a-pa-seo ya-geul meo-geo-sseo-yo.
Use -aseo after a stem whose final vowel is ㅏ or ㅗ (아프다 → 아파서). Cause leads to action.
늦어서 미안해요.
I'm sorry because I'm late.
neu-jeo-seo mi-an-hae-yo.
Here -eoseo is used after a stem ending in a consonant (늦다 → 늦어서); it gives a reason for an apology.
비가 오니까 우산을 가져가세요.
Because it's raining, please take an umbrella.
bi-ga o-ni-kka u-san-eul ga-jyeo-ga-se-yo.
Use -nikka to give a reason for a suggestion or command. More direct than -aseo.
내일 시험이 있으니까 오늘 공부해야 해요.
Because I have an exam tomorrow, I have to study today.
nae-il si-heo-mi i-sseu-ni-kka o-neul gong-bu-hae-ya hae-yo.
Use -nikka when the reason is important for the listener to know. Often used in explanations.
Pronunciation guides are approximate. Slow playback keeps the original pitch.
Make it make sense
Useful pattern
To connect a cause and a result, attach -aseo/-eoseo to the verb stem of the cause clause. The choice between -aseo and -eoseo depends on the final vowel of the stem: use -aseo after ㅏ or ㅗ, and -eoseo after all other vowels (including stems ending in a consonant, where the ending is -어서). For example, 오다 (to come) becomes 와서 (o-da → wa-seo), and 먹다 (to eat) becomes 먹어서 (meok-da → meo-geo-seo). This ending means 'so' or 'because' and implies a natural, sequential result. In contrast, -nikka is added to the stem regardless of vowel, but it often carries a nuance of giving a reason or justification, as in 비가 오니까 (bi-ga o-ni-kka, 'because it's raining'). Note that -nikka can be used with suggestions or commands, while -aseo/-eoseo cannot.
When to use it
Use -aseo/-eoseo when the second clause is a direct, natural consequence of the first, and you are simply stating a fact. For example, 피곤해서 잤어요 (pi-gon-hae-seo ja-sseo-yo, 'I was tired, so I slept'). Use -nikka when you want to emphasize the reason, especially when giving a justification, making a suggestion, or when the listener might not know the reason. For instance, 내일 시험이 있으니까 공부해야 해요 (nae-il si-heo-mi i-sseu-ni-kka gong-bu-hae-ya hae-yo, 'Because I have an exam tomorrow, I have to study'). Also, remember that -aseo/-eoseo cannot be used with imperative or propositive endings (like -세요 or -ㅂ시다), but -nikka can: 비가 오니까 우산을 가져가세요 (bi-ga o-ni-kka u-san-eul ga-jyeo-ga-se-yo, 'Because it's raining, please take an umbrella').
Listen to each line, then take one part and reply out loud.
왜 집에 있었어요?
Why were you at home?wae ji-be i-sseo-sseo-yo?비가 와서 집에 있었어요.
It rained, so I stayed home.bi-ga wa-seo ji-be i-sseo-sseo-yo.내일 시험이 있으니까 오늘 공부해야 해요.
Because I have an exam tomorrow, I have to study today.nae-il si-heo-mi i-sseu-ni-kka o-neul gong-bu-hae-ya hae-yo.그럼, 같이 공부해요.
Then let's study together.geu-reom, ga-chi gong-bu-hae-yo.A little context goes a long way
In Korean, the choice between -aseo/-eoseo and -nikka can reflect politeness and social distance. -aseo/-eoseo is neutral and common in both polite and casual speech. -nikka can sound more assertive or explanatory, so in formal situations it may be softened with the polite particle -yo, as in -nikka-yo. When speaking to superiors, using -nikka with a command can be rude; instead, use a softer expression or indirect phrasing. Koreans also often use -aseo/-eoseo to avoid sounding blunt when giving reasons.
One thing to watch for
Using -aseo/-eoseo with a command or suggestion, as in *비가 와서 우산을 가져가세요.
Try this instead: Use -nikka instead: 비가 오니까 우산을 가져가세요 (bi-ga o-ni-kka u-san-eul ga-jyeo-ga-se-yo). -aseo/-eoseo cannot be followed by imperative or propositive endings, while -nikka can express a reason for a command.
Your turn
Try answering out loud before checking a possible answer.
1Combine the two sentences using -aseo/-eoseo: 배가 아프다 (stomach hurts) + 약을 먹었어요 (took medicine).
Show a sample answer
배가 아파서 약을 먹었어요.
The verb 아프다 ends in a vowel, so use -aseo: 아파서. This shows a natural result. Alternative: 배가 아프니까 약을 먹었어요 is also possible but emphasizes the reason more.
2Which ending would you use to give a reason for a suggestion: -aseo/-eoseo or -nikka? Provide an example.
Show a sample answer
-nikka, e.g., 비가 오니까 우산을 가져가세요.
Because -aseo/-eoseo cannot be used with commands or suggestions, -nikka is correct. The sentence means 'Because it's raining, please take an umbrella.'
3Translate into Korean: 'I was busy, so I couldn't call.' Use 바쁘다 (to be busy) and 전화하다 (to call).
Show a sample answer
바빠서 전화 못 했어요.
바쁘다 becomes 바빠서 (stem ends in vowel). The negative 못 했어요 means 'couldn't do'. Alternative: 바쁘니까 전화 못 했어요 is also correct but gives a stronger reason.
Use -aseo/-eoseo for natural results ('so') and -nikka for reasons or justifications ('because'). Remember that -aseo/-eoseo cannot be used with commands, but -nikka can.
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