Morphological Causative -우-

-우- is the causative suffix that lives on vowel-final stems. It turns 깨다 ("wake up," intransitive) into 깨우다 ("wake someone up"), 자다 ("sleep") into 재우다 ("put to sleep"), and 크다 ("be big / grow") into 키우다 ("raise, bring up"). It is one of the seven fused causative infixes (이/히/리/기/우/구/추), and it is the one English speakers meet earliest, because its members are some of the most-used verbs in daily life — you wake someone, feed the fire by burning something, raise a child, set up a plan. The catch, and the whole reason this page exists, is that several of the highest-frequency -우- verbs do not simply glue 우 onto the plain stem — the stem itself changes shape (서→세, 자→재, 타→태). Those have to be learned as fixed vocabulary, not generated on the fly.

How -우- builds a causative

For the well-behaved members, you take the stem, add 우, and add the ending: 깨 + 우 + 다 → 깨우다. The base verb's subject becomes the object of the new transitive verb — the person who wakes up becomes the person you wake.

Conjugation is completely regular for a 우다-stem: the 우 contracts with a following -어 into 워, so present is 깨워요 (kkaewoyo) and past is 깨웠어요 (kkaewosseoyo). Compare the plain 깨다: 잠에서 깼어요 ("I woke up") versus the causative 저를 깨웠어요 ("[someone] woke me up").

The -우- inventory

The top three (깨우다, 비우다, 지우다) are the transparent ones: the stem is unchanged and 우 simply attaches. 비우다 comes straight from 비다 and shows up everywhere — 잔을 비우다 ("empty a glass," i.e. drink up), 마음을 비우다 ("empty one's mind," let go of ambition), 자리를 비우다 ("step away from one's seat, be out").

The irregular four: a hidden double causative

Now the hard part, told honestly. In 세우다, 재우다, 태우다, and 키우다 the stem vowel changes — 서→세, 자→재, 타→태, 크→키 — and there is a real reason for it. Historically these are not one causative suffix but two stacked together: an older 이 plus 우 (이+우). That first 이 raised or fronted the stem vowel before fusing away, and the raised vowel is what survives today:

You do not need this history to use the verbs, but it explains why you cannot just paste 우 onto the plain stem and why ×자우다 and ×서우다 are wrong. The vowel change is baked in.

세우다: one verb, a fan of meanings

세우다 is worth a section by itself because it spreads far beyond "make stand." Its core is bring something to a standing / stopped / established state, and Korean runs that metaphor a long way:

• 차를 세우다 — stop / pull over / park a car
• 건물을 세우다 — put up a building
• 회사를 세우다 — found a company
• 계획을 세우다 — draw up a plan
• 기록을 세우다 — set a record
• 원칙을 세우다 — establish a principle

Notice that English uses a different verb for each of these — stop, put up, found, draw up, set — where Korean reuses the single causative 세우다. This is the mirror image of the situation English learners usually expect, and a good reminder that the "make X" gloss is only a starting point.

태우다: two verbs sharing one shape

태우다 is really two causatives that happen to look identical, because the base 타다 is itself two verbs. 타다 means both "ride" and "burn (intransitive)," so 태우다 means both:

• 사람을 태우다 — give someone a ride, pick someone up (from 타다 "ride")
• 종이를 태우다 / 밥을 태우다 — burn paper / scorch the rice (from 타다 "burn")

There is even a third, idiomatic 태우다 — 애를 태우다 / 애태우다 ("make [someone] anxious," literally "burn the guts"). Context and the object noun always tell the three apart, so learn them together as a small family rather than reasoning from the base each time.

Common Mistakes

1. Regularizing the stem of 재우다 / 세우다. The vowel change is obligatory; ×자우다, ×서우다 do not exist.

2. Using the base 크다 as a transitive "raise." 크다 is intransitive ("grow, be big"); to raise a child or an animal you need 키우다.

3. Using intransitive 타다 to give someone a ride. You board a car yourself with 타다, but to seat someone else in it you need the causative 태우다.

4. Using 깨다 where you mean 깨우다. 깨다 is "wake up (by oneself)"; waking someone else is 깨우다.

Key Takeaways

• -우- is the causative suffix for vowel-final stems: 깨우다, 비우다, 지우다, 세우다, 재우다, 태우다, 키우다.
• The transparent members (깨우다, 비우다, 지우다) just add 우; the irregular four (세우다, 재우다, 태우다, 키우다) come from an old double causative 이+우 and carry a stem-vowel change — memorize them.
• 세우다 fans out to stop / build / found / draw up / set (a record); 태우다 is both "give a ride" and "burn," from the two 타다 bases.
• The commonest error is regularizing the stem (×자우다, ×서우다) or reaching for the intransitive base (타다, 크다) instead of the causative.