Attaching 아\어 particles to verbs & adjectives

There are many grammatical particles that come up in my lyric lessons that look like this: “-아… / -어…”. This means that you have to choose either the particle that begins with 아 or the one that begins with 어 when attaching the particle to a verb or adjective.


-아버리다 / -어버리다 = “to go and do X”, “to completely X”

-아야 하다 / -어야 하다 = “to have to do X”

-아주다 / -어주다 = adds a nuance of “as a favour to” the object of the sentence

-아도 / -어도 = “even if X happens”

-아 / -어 = present tense verb conjugation in 반말 (casual language)

-았어 / -었어 = this is the past tense ending in 반말

For the examples in this lesson, we’ll use that last particle – the past tense one.

But how do you know which version to choose?

We’ll work with 9 example words in this lesson. And the first thing we’ll do with them is chop the 다 off the end to find the root.

몰다to drive
걸다to hang (something)
불다to blow
나오다나오to come out
가다to go
주다to give
보이다보이to be seen, to be visible
결정하다결정하to decide
바쁘다바쁘to be busy

The basic rule of 아/어 additions is this: if the last syllable of the root to which you’re adding the particle contains ㅗ or ㅏ you attach the 아 version. If it’s anything else, you attach the 어 version.

But there are a few other factors that come into play. Let’s look at them one by one through our example words:

  1. 몰다
    Root: 몰
    Particle to add: -았어
    Final result: 몰았어
    Meaning: “I drove.”
  2. 걸다
    Root: 걸
    Particle to add: -었어
    Final result: 걸었어
    Meaning: “I hung [it].”
  3. 불다
    Root: 불
    Particle to add: -었어
    Final result: 불었어
    Meaning: “I blew.”
  4. 나오다. Here’s where it gets interesting.
    Root: 나오
    Particle to add: -았어. Nothing new so far. But since the last syllable of 나오 ends in a vowel, we’ll actually merge our particle with it instead of adding it on to the end.
    Final result: not 나오았어, but 나왔어.
    Meaning: “I came out.” or “Here I am.”
  5. 가다
    Root: 가
    Particle to add: -았어. This is in essence the same as 나오다, except that the two vowels we’re merging are the exact same, so the merge doesn’t alter our root.
    Final result: 갔어
    Meaning: “I went.”
  6. 주다
    Root: 주
    Particle to add: -었어. This is the same idea as 나오다 and 가다. Because our root ends in a vowel, we merge.
    Final result: 줬어
    Meaning: “I gave [it].”
  7. 보이다
    Root: 보이
    Particle to add: -었어. Again we merge. How does “ㅣ” merge with ㅓ? Like this: ㅕ.
    Final result: 보였어
    Meaning: “It shows/it’s visible/I can see it.”
  8. 결정하다. This one is interesting. Many verbs end in 하다. The root is 하, so of course:
    Particle to add: -았어. But when 아 merges with 하, something interesting happens. It turns into 해.
    Final result: 결정했어
    Meaning: “I decided.”
  9. 바쁘다. The weirdest yet. When the vowel in the last syllable of a root is “ㅡ” you don’t use that syllable to determine whether to add 아 or 어, you use the previous syllable. In this case, that syllable contains ㅏ so:
    Particle to add: -았어. (If there is no previous syllable, in other words if the root is only 1 syllable in length, choose the 어 version of the particle.) Additionally, when the “ㅡ” syllable does not end with a consonant, we don’t merge like we did with 나오다, 갇, and 주다. We replace the “ㅡ” with our particle.
    Final result: 바빴어
    Meaning: “I was busy.”

Handy chart form? Yes please!



You may remember that I promised you there are no inexplicable grammatical exceptions in Korean? Well, that’s almost true. (There are VERY few). However, there are irregular letters that follow their own rules when adding grammatical principles. I won’t teach them to you, because I want you to like me. But if you want to give yourself a proper headache and maybe have a good cry, get in-depth with it at

adding endings to verbs Korean