-아/어 두다: Doing It in Advance and Keeping It

Korean has a whole family of auxiliary verbs that attach to a main verb's -아/어 form and add a layer of meaning about how or why the action is done. -아/어 두다 is the one that says: I did this now, on purpose, so that the result is ready and waiting for later. The main verb tells you the action (buy, put, write, learn); 두다 — literally "place / keep / leave" — tells you the result has been set aside for the future. English has no single word for this, which is exactly why learners either skip it or reach for the wrong auxiliary. This page fixes both problems.

The core idea: do it now, keep it for later

On its own, 두다 is an ordinary verb meaning "to place" or "to keep" (책상 위에 두다 "put it on the desk"). As an auxiliary, it keeps that "keep it there" flavor but applies it to the result of the main action. You do the action once, and the outcome persists — deliberately — because you'll want it later.

Notice that 뒀어요 is just the contracted past of 두었어요 (두 + 었 → 뒀). In all three, the point isn't merely that I bought / made / put — it's that I did it ahead of time and left it in a ready state. Strip the 두다 out (표를 샀어요) and you lose that "it's now waiting for us" nuance that a Korean speaker would want here.

How to form it

Attach 두다 to the main verb's -아/어 form, following the ordinary vowel-harmony rule, then conjugate 두다 for tense and politeness (the main verb freezes; only 두다 inflects).

The present 두어요 usually contracts to 둬요, and the past 두었어요 to 뒀어요 — the contracted forms are what you actually say and write. The imperative 두세요 / 둬 and the conditional 두면 are all extremely common, because so much of this construction's life is telling someone (or reminding yourself) to get something ready.

Why 두다, not 놓다: the "storage" nuance

Korean has a near-twin, -아/어 놓다, that also means "do X and leave the result." For many physical, just-completed actions the two genuinely overlap (문을 열어 놓다 ≈ 열어 두다). But 두다 leans harder on deliberate keeping for the future — you set the result aside on purpose so you can use it later. 놓다 leans on the state simply existing right now as a consequence of what you just did.

That difference is invisible until you hit mental and preparatory verbs, where only 두다 works:

You learn something once and keep it stored for the exam — a perfect fit for 두다's "bank it for later" logic. Say ×알아 놓아 instead and a native ear flinches: knowing isn't a physical result you "leave lying around," it's a resource you stockpile. The same goes for 기억해 두다 ("keep in memory"), 명심해 두다 ("bear firmly in mind"), and 외워 두다 ("memorize for later"). All of them are about laying in a mental supply for the future — 두다 territory.

It pairs with 미리 and future-facing context

Because the whole point is preparation, -아/어 두다 clusters with words like 미리 ("beforehand"), 나중을 위해 ("for later"), 혹시 몰라서 ("just in case"), and clauses like "before X happens." If you see any of those, 두다 is very often the auxiliary you want.

English contrast: the missing auxiliary

English collapses all of this into a bare verb plus, at most, an adverb: "I bought the tickets," "I've booked a hotel," "make sure you learn it." There is no grammatical slot in English that says and I'm leaving the result ready for the future. The closest analogues are phrasal verbs like "stock up," "set aside," "line up," or "keep (something) in mind" — but those are lexical choices, not a productive pattern you can bolt onto any verb. Korean 두다 is that productive pattern: any action verb can take it, and the "…for later" meaning is added automatically. This is precisely why English speakers under-use it — nothing in their native grammar prompts them to reach for it, so they say the bare 표를 샀어요 where a Korean speaker's instinct is 표를 사 뒀어요.

Note also the spacing: standard orthography writes the auxiliary separately (사 두다), though the joined 사두다 is also permitted. Keep the space; it's the safer, more common convention and it makes the two-verb structure visible.

Common Mistakes

1. Using 놓다 for mental or preparatory verbs. "Keep it in mind for later" is 두다's job, not 놓다's.

2. Dropping the auxiliary where Korean wants the "ready for later" framing. Not ungrammatical, but it flattens the meaning your listener expects.

3. Inflecting the main verb instead of 두다. Only the auxiliary carries tense and politeness; the main verb stays frozen in its -아/어 form.

4. Using 두다 for a fleeting action with no future payoff. 두다 implies you're keeping the result for something. A truly momentary, no-consequence action just takes the plain verb.

Key Takeaways

• -아/어 두다 = do the action now and deliberately keep the result ready for later use; it pairs naturally with 미리 and "before X" contexts.
• Form it on the main verb's -아/어 form; conjugate only 두다 (present 둬요, past 뒀어요, imperative 두세요/둬).
• Mental and preparatory verbs take 두다, not 놓다: 알아 두다, 기억해 두다, 외워 두다 — you're stockpiling a resource for the future.
• English has no equivalent auxiliary, so English speakers systematically under-use it; train yourself to add it whenever the sense is "…and now it's ready."
• When 두다 and 놓다 are both grammatical, 두다 adds "for later," 놓다 adds "as it now is" — see the 놓다 vs 두다 comparison.