English lumps a whole range of "adding" words together — also, too, as well, in addition, moreover, plus, what's more, on top of that — and lets tone and context sort them out. Korean splits the job across a small set of conjunctions that differ along two axes: formality (casual vs. written) and rhetorical push (a neutral "and also" vs. an escalating "and to make it stronger"). The three core members form a rising ladder: 또 (light, everyday), 또한 (formal, writing), and 게다가 (escalating, "what's more"). Unlike the 그렇다-derived conjunctions, these are ordinary adverbs — no 그렇다 inside, no allomorphy, nothing to conjugate.
또: the light, spoken "also"
또 is the everyday "also / and also" of conversation. It is short, unpretentious, and adds one more same-direction point without ceremony.
그는 똑똑해요. 또 성실해요.
geuneun ttokttokaeyo. tto seongsilhaeyo
He's smart. He's also hardworking.
또 has a second, even more common life as a bare adverb meaning "again" — and this double duty is a genuine trap, because the same word can read either way (see the mistakes below).
또 오세요.
tto oseyo
Come again. (please visit again)
또 also loves to sit alongside the "also" particle 도, reinforcing a growing list — "no money, and no time either":
돈도 없고, 또 시간도 없어요.
dondo eopgo, tto sigando eopseoyo
I have no money, and no time either.
아까 전화했는데 또 문자도 보냈어요.
akka jeonhwahaenneunde tto munjado bonaesseoyo
I called earlier, and I also sent a text.
또한: the formal, written "as well"
또한 is a register step up (formal, written). It means "also / as well / likewise" and is at home in essays, reports, presentations, and formal speech — the places where bare 또 would sound too light. It is also more mobile: 또한 can sit at the head of the sentence or slot in mid-sentence.
저는 학생입니다. 또한 회사에도 다닙니다.
jeoneun haksaeng-imnida. ttohan hoesaedo danimnida
I am a student. I also work at a company. (formal 합니다체)
이 제품은 저렴하고 또한 튼튼합니다.
i jepumeun jeoryeomhago ttohan teunteunhamnida
This product is inexpensive and also sturdy. (formal, 또한 mid-sentence)
The examples above use the formal 합니다체 deliberately — that is the register 또한 belongs to. Drop 또한 into casual banmal and it clashes; there, 또 or 그리고 is what you want.
게다가: the escalating "what's more"
게다가 is different in kind, not just in register. It means "on top of that / what's more / besides," and it adds a same-direction point that raises the stakes — piling a further reason onto an already-established slant, whether good or bad. It carries a rhetorical push the others lack: "and as if that weren't enough…".
비가 왔어요. 게다가 바람도 심했어요.
biga wasseoyo. gedaga baramdo simhaesseoyo
It rained. On top of that, the wind was terrible too.
이 집은 위치도 좋아요. 게다가 월세도 싸요.
i jibeun wichido joayo. gedaga wolsedo ssayo
This place has a great location. And on top of that, the rent is cheap too.
Notice the direction stays constant: first a bad thing (rain), then a worse thing (wind); or first a plus (location), then another plus (cheap rent). 게다가 never pivots to a contrast — it only intensifies the existing lean. Like 또, it pairs naturally with 도 on the added item (바람도, 월세도).
Reframing for English speakers
English "also / moreover / plus / on top of that" all point the same rough direction, so learners grab whichever Korean word they learned first — usually 또 — and use it everywhere. But 또 is spoken and light; using it in writing where you mean "moreover" makes the prose sound bare and unpolished. Match the Korean word to the job: neutral spoken addition → 또; formal written addition → 또한; escalating "what's more" → 게다가. For the strongest "and what's even more," Korean reaches further still — to 더구나 and 그 외에, covered on the 더구나 page.
Common Mistakes
1. Using bare 또 in writing where you mean "moreover / furthermore." In formal prose, 또 is too light; use 또한 or 게다가.
❌ 이 방법은 효율적이다. 또 비용이 적다.
Too bare for writing — for 'moreover,' use 또한/게다가.
✅ 이 방법은 효율적이다. 또한 비용도 적다.
i bangbeobeun hyoyuljeogida. ttohan biyongdo jeokda
This method is efficient. It is also low in cost. (written 한다체)
2. Using 게다가 to introduce a contrast. 게다가 only escalates in the same direction; it never pivots to an opposite point. For contrast, use 하지만/그런데.
❌ 이 식당은 서비스가 좋아요. 게다가 값은 비싸요.
Wrong — good service (a plus) and high prices (a minus) pull in opposite directions. 게다가 only escalates the same direction; it can't pivot to a contrast.
✅ 이 식당은 서비스가 좋아요. 그런데 값은 비싸요.
i sikdang-eun seobiseuga joayo. geureonde gapseun bissayo
This restaurant has good service. But the prices are high.
3. Relying on bare 또 for "(someone) also," when it reads as "again." 또 alone before a verb defaults to "again"; to mean "X too," mark X with 도.
❌ 그 사람 또 왔어요.
This reads as 'that person came again,' not 'that person also came.'
✅ 그 사람도 왔어요.
geu saramdo wasseoyo
That person came too. (mark the added person with 도)
4. Using formal 또한 in casual conversation. 또한 belongs to writing and formal speech; in banmal chat it sounds stiff. Use 또 or 그리고.
❌ 나 배고파. 또한 졸려.
Register clash — 또한 is formal/written; casual speech wants 또/그리고.
✅ 나 배고파. 그리고 졸려.
na baegopa. geurigo jollyeo
I'm hungry. And I'm sleepy. (casual)
Key Takeaways
- The additive conjunctions form a register-and-force ladder: 또 (light, spoken "also") < 또한 (formal, written "as well") < 게다가 (escalating "on top of that / what's more").
- 또 doubles as "again" as a bare adverb (또 오세요) — a real ambiguity; force "also" by marking the added item with 도.
- 또한 is more mobile (front or mid-sentence) and belongs to formal/written register.
- 게다가 adds a same-direction point that raises the stakes — never a contrast (that's 하지만/그런데).
- These are plain adverbs, not 그렇다-derived: no allomorphy, no conjugation. For a stronger "what's more," see 더구나 / 그 외에.
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- 그리고: And / And ThenTOPIK 1 — The most basic conjunction, 그리고 joins two sentences as 'and' (adding a fact) or 'and then' (sequence) — with its ending twin -고 that fuses clauses inside one sentence, and a warning about the number-one learner error: gluing every sentence with 그리고.
- 더구나 · 그 외에(도): What's More / BesidesTOPIK 3 — The strong additive conjunctions — 더구나 stacks a further point in the same direction (usually with emotional weight), while 그 외에(도) enumerates items beyond an already-named set. English 'moreover / besides' blurs the two.
- Sentence Conjunctions 접속부사 and the 그렇다 PatternTOPIK 1 — The words that open a sentence and link it to the last one — 그리고, 그래서, 하지만, 그런데 — and the single insight that unlocks almost all of them: most are 그렇다 ('be so') plus a connective ending, so each conjunction has an ending twin.
- 도: Also, Too, EvenTOPIK 1 — 도 is the additive particle 'also, too, as well' (and, on a scale, 'even'). It has no allomorphy, it REPLACES the subject/object markers 이/가 and 을/를, and it STACKS on top of every other particle.