A college degree does not protect you from Korean spelling errors. Neither does a decade of professional experience. These 10 mistakes appear in emails, reports, and Kakao messages every single day — written by intelligent, educated people who simply never learned the underlying rules.

This isn't a memory exercise. Each entry explains the principle. Understand the rule once and you'll stop making the mistake permanently.

1. 됐다 vs 됬다

Correct: 됐다

"됐다" is the contracted form of "되었다" (it happened / it worked out). The contraction 되었다 → 됐다 follows regular rules. "됬다" does not exist in Korean. The confusion comes from the way 됐다 sounds when spoken quickly. Verification rule: substitute "되었다" — if the sentence is natural, "됐다" is correct.

2. 어떡해 vs 어떻게

Both are correct — in different contexts

"어떡해" is a contraction of "어떻게 해" (what do I do / how terrible). It appears at the end of a sentence expressing distress or surprise. "어떡해, 이게 무슨 일이야?" / "어떻게" is an adverb meaning "how" or "in what way." It precedes a verb. "어떻게 하면 될까?" The test: if you could complete the sentence with "해야 해," use "어떡해." If a verb follows, use "어떻게."

3. 왠지 vs 웬지

Correct: 왠지

"왠지" (왜인지 contracted) means "for some reason" or "inexplicably." It describes a feeling without a clear cause. "웬" means "what kind of" or "which" — it appears in "웬 말이야" (what are you talking about?) or "웬 떡이냐" (what luck!). They sound similar but are semantically different. If you mean "for some reason," it is always 왠지.

4. 안 vs 않

Placement determines the choice

"안" is a short negation adverb that precedes the verb directly: "안 먹었다" (didn't eat), "안 좋다" (not good). "않" is a suffix from "아니하다" and attaches after a verb stem: "먹지 않았다," "좋지 않다." Quick test: can you replace the word with "아니하"? If yes, use "않." If it would sound absurd (안 → 아니하), use "안."

5. 것 같다 — spacing

Correct: 것 같다 (with a space)

"것" is a dependent noun (의존명사) and must be written with a space before it: "맞는 것 같다" — not "맞는것 같다." In casual digital communication the spacing is often dropped, which has trained people to see the attached version as normal. In formal writing, the space is mandatory.

6. 로서 vs 로써

Different grammatical roles

"로서" marks capacity, status, or identity: "부모로서 책임이 있다" (as a parent, there is responsibility). "로써" marks means, method, or material: "대화로써 해결하자" (let's resolve it through dialogue). Memory trick: "써" relates to using something ("쓰다" = to use), so 로써 = using [X] as a method.

7. 며칠 vs 몇일 / 몇 일

Correct: 며칠

"며칠" is the correct form, meaning "how many days" or "what day of the month." Although it evolved from 몇+일, the phonological change resulted in a fixed spelling of 며칠. Neither "몇일" nor "몇 일" is standard. This is an exception — simply memorize it.

8. 이따가 vs 있다가

Both exist — different meanings

"이따가" is a time adverb meaning "a little later" or "in a bit": "이따가 전화해." "있다가" describes staying somewhere and then leaving: "집에 있다가 나왔다" (was at home and then came out). If "a little later" fits the meaning, use 이따가. If the action involves being present somewhere first, use 있다가.

9. 역할 vs 역활

Correct: 역할

"역할" (role) is correct. "역활" does not exist. The confusion is entirely phonological — the way 역할 sounds leads some writers to assume the ending must be "활." There is no 활 here. Just memorize: 역할, not 역활.

10. 오랫동안 vs 오래동안

Correct: 오랫동안

"오랫동안" is the correct form (for a long time). The sai-siot (ㅅ) is inserted between 오래 and 동안 because of the phonological rule for compound nouns where the first element ends in a vowel and the second begins with a specific consonant. The resulting pronunciation resembles "오랟똥안." Spelling: always 오랫동안.

Score Yourself

8–10 correct in daily usage: you write with real precision. Under 4: these rules are worth revisiting carefully. Most adults sit in the 5–7 range — knowing some intuitively but uncertain about the edge cases.

The good news: once you understand the rule behind each mistake, you don't need to memorize it. The logic sticks.