In short

A helping verb stacked behind the main verb adds how an action finished. -아/어 버리다 = it is done and gone (relief or regret): 다 먹어 버렸어요 (ate it all up). -고 말다 = it ended that way against your will: 결국 울고 말았어요 (I ended up crying). -아/어 놓다 / -아/어 두다 = you did it and left the result standing: 창문을 열어 놓았어요 (I opened the window and left it open). -아/어 가다 / -아/어 오다 = it moves through time, away from or toward now.

The rule

Each of these is a main verb followed, with a space, by a second verb that has bleached into a helper. The helper carries the tense and ending; the main verb supplies the meaning.

Step 1 - -아/어 버리다: it is completely done and gone

Take the 아/어 form of the verb (lesson 10) and add 버리다 (beorida, literally throw away):

Verb’s 아/어 form + 버리다 -> 먹어 버렸어요, 가 버렸어요, 해 버렸어요

It says the action is finished with nothing left over, and adds a feeling. Two flavours, decided by context: relief - a burden is gone (숙제를 다 해 버렸어요, I got all the homework done and off my plate) - or regret - something you wanted is gone (친구가 가 버렸어요, my friend went and left). The adverb 다 (da, all, completely) pairs with it constantly. It attaches to transitive and intransitive verbs alike. Note: 잊다 (forget) and 잃다 (lose) fuse into the single lexical words 잊어버리다 and 잃어버리다 - written with no space.

Step 2 - -고 말다: it ended that way despite you

Attach -고 말다 to the plain stem and conjugate 말다: it is invariant like -고 있다 - no 아/어 choice, no 으, no 받침 rule.

Verb stem + 고 말다 -> 울고 말았어요, 지고 말았어요, 떠나고 말았어요

It marks an unintended, usually unwelcome end result - the outcome arrived on its own and you could not stop it. It loves the adverbs 결국 (gyeolguk, in the end) and 그만 (geuman, without meaning to), and it leans toward intransitive, uncontrolled verbs: 울다, 지다, 떨어지다 (fall; fail an exam), 넘어지다 (fall over). The 국립국어원 dictionaries define the helper as the action 끝내 실현됨 (coming about in the end) - most often with regret, but they also record a positive “and I pulled it off at last” reading. That proud reading normally wants the emphatic -고야 말다 or the resolve form -고 말겠다: 기어이 해내고야 말았어요 (I finally went and pulled it off). Bare -고 말다 with no 야 defaults to regret.

Step 3 - -아/어 놓다 / -아/어 두다: do it and leave the result standing

Take the 아/어 form and add 놓다 (nota) or 두다 (duda). Both mean do something to an object and leave that result in place for later, so both need a transitive verb:

Object + 을/를 + Verb’s 아/어 form + 놓다 / 두다 -> 창문을 열어 놓았어요, 표를 사 두었어요

The nuance: 두다 leans “keep in reserve for future use” (미리 사 두세요 buy it in advance, 알아 두세요 keep it in mind); 놓다 leans “set the immediate result in place” (열어 놓다 leave open, 켜 놓다 leave switched on). They overlap heavily; for “prepare ahead,” 두다 is the safer pick. This is the deliberate cousin of the observed state -아/어 있다 (lesson 32): 문이 열려 있어요 just reports an open door, while 문을 열어 놓았어요 says someone opened it on purpose and left it.

Step 4 - -아/어 가다 / -아/어 오다: progression through time

Take the 아/어 form and add 가다 (go) or 오다 (come). The physical come/go turns into a timeline: 오다 = the process ran up toward now (지금까지 일해 왔어요, I have worked up to now); 가다 = it moves onward into the future (다 되어 가요, it is getting done; 늙어 가요, is growing old).

Step 5 - keep these apart from the neighbours

Same window, five aspects (see the contrast table): plain past is the bare fact, -고 있다 is the action in progress, -아/어 있다 is an intransitive state simply observed, -아/어 놓다 is a transitive result left on purpose, and -아/어 버리다 is the action driven to completion with feeling.

Forms & patterns

The four auxiliaries at a glance:

The 아/어 choice (shared by 버리다, 놓다, 두다, 가다, 오다):

-고 말다 - invariant, plain stem (no 아/어):

Same window, five aspects:

Examples

Common mistakes

• 다 먹고 버렸어요. (da meokgo beoryeosseoyo.) -> 다 먹어 버렸어요. (da meogeo beoryeosseoyo.) - The completion helper needs the 아/어 form: 먹어 버리다. With -고 it means “ate it and then threw it away” - two separate actions.
• 울어 말았어요. (ureo marasseoyo.) -> 울고 말았어요. (ulgo marasseoyo.) - -고 말다 attaches to the plain stem with -고, never the 아/어 form. It is invariant, exactly like -고 있다.
• 비밀번호를 잊어 버렸어요. (bimilbeonhoreul ijeo beoryeosseoyo.) -> 비밀번호를 잊어버렸어요. (bimilbeonhoreul ijeobeoryeosseoyo.) - 잊어버리다 and 잃어버리다 are single headwords in 표준국어대사전 (잊어-버리다), so they carry no space, unlike the productive helper in 먹어 버리다.
• 문이 열어 놓았어요. (muni yeoreo noasseoyo.) -> 문을 열어 놓았어요. (muneul yeoreo noasseoyo.) - -아/어 놓다 is transitive: you act on an object, so it is marked 을/를 (문을). If you only mean the resulting state “the door is open,” use the intransitive 문이 열려 있어요.

Tips

• 버리다 = “off / up / away,” and the feeling rides on context. 다 먹어 버렸어요 can be relief (finished it off, phew) or regret (it’s all gone); 잃어버렸어요 is pure regret. Same form, tone from the situation.
• 말다 is usually fate, not a boast. It pairs with 결국 (in the end) and 그만 (accidentally) and reports an outcome that happened to you. The proud “I got there in the end” reading does exist, but it wants the emphatic -고야 말다 (기어이 이기고야 말았어요, we finally went and won) or the resolve form -고 말겠다; for a plainly happy result, drop the helper and use the plain past (성공했어요).
• 놓다 vs 두다. Both are “do it and leave it,” but 두다 leans toward keeping something for later use - 사 두다 (buy for later), 알아 두다 (keep in mind) - while 놓다 leans toward setting the immediate result in place - 열어 놓다, 켜 놓다. For “prepare ahead,” reach for 두다.
• 가다/오다 on a timeline. 오다 pulls the process toward now (일해 왔어요, have worked up to this point); 가다 pushes it onward (다 되어 가요, getting done; 늙어 가다, growing old). It is just physical come/go mapped onto time.