In short

Roughly 60% of Korean vocabulary is 한자어 (hanjaeo) - words built from Chinese roots, written in ordinary 한글. They snap together from a small set of reusable prefixes (불-, 비-, 무-, 재-, 초-…) and suffixes (-적, -화, -성, -력, -자, -용…). Learn the pieces and you can decode compounds you have never seen - which is exactly why this lesson is an accelerator for reading, not a structural must.

The rule

This lesson is marked optional / advanced: nothing here is a new sentence pattern. It is vocabulary machinery. The payoff is word-attack - meeting 세계화 (segyehwa) for the first time and reading it as 세계 (world) + -화 (-ization) = “globalization” without a dictionary.

Step 1 - Prefixes attach to the FRONT of a 한자어 noun

Each prefix carries a fixed meaning and glues straight onto a noun with no particle and no space: Prefix + Noun.

• 불- (bul-, not / un-): 가능 (ganeung, possible) -> 불가능 (bulganeung, impossible).
• 비- (bi-, non-): 공식 (gongsik, official) -> 비공식 (bigongsik, unofficial).
• 무- (mu-, -less, without): 무료 (muryo, free of charge), 무관심 (mugwansim, indifference).
• 미- (mi-, not yet): 완성 (wanseong, completion) -> 미완성 (miwanseong, unfinished).

One sound rule to know: 불- drops its ㄹ and becomes 부- before a root starting in ㄷ or ㅈ - 부동산 (budongsan, real estate), 부정 (bujeong, injustice), 부족 (bujok, shortage), not *불동산, *불정, *불족.

Step 2 - Suffixes attach to the BACK and often change the word class

Suffixes are where the real leverage is, because several of them turn a plain noun into a new part of speech.

• -적 (-jeok) makes an adjectival noun: 사회 (sahoe, society) -> 사회적 (sahoejeok, social). It then behaves like a noun in three slots - see the Tips.
• -화 (-hwa, -ization): 국제 (gukje, international) -> 국제화 (gukjehwa, internationalization). It readily takes 되다/하다: 국제화되다 (to become internationalized).
• -성 (-seong, -ness, -ity): 가능 -> 가능성 (ganeungseong, possibility).
• -력 (-ryeok, power, ability): 경쟁 (gyeongjaeng, competition) -> 경쟁력 (gyeongjaengnyeok, competitiveness).
• -자 (-ja, person), -원 (-won, staff), -실 (-sil, room), -장 (-jang, head/chief): 참가 -> 참가자, 직 -> 직원, 사무 -> 사무실, 사(社) -> 사장.
• -법 (-beop, method), -용 (-yong, for use in), -간 (-gan, interval), -중 (-jung, in the middle of).

The -률/율 pair (rate) picks its shape by the preceding sound, just like a particle: -율 after a vowel or a ㄴ 받침 (비율 biyul, 출산율 chulsannyul), -률 everywhere else (성공률 seonggongnyul, 확률 hwangnyul).

Step 3 - 하다 / 되다 / 시키다 turn a 한자어 noun into a verb

This is the single most productive engine in the language. A two-syllable 한자어 noun + one of three light verbs gives you a full verb, and the choice sets the voice:

Noun + 하다 = do it (active) - Noun + 되다 = it happens / gets done (passive/inchoative) - Noun + 시키다 = make someone do it (causative).

발전 (baljeon, development) -> 발전하다 (develop) / 발전되다 (be developed) / 발전시키다 (develop something). All three are written solid, as one word: 공부하다, never *공부 하다.

Step 4 - Register: 한자어 is the formal twin of a native word

Many everyday ideas have two words - a plain native one (고유어) and a formal, often Sino-Korean, one. Reach for the 한자어 in writing, business, and polite speech: 식사 over 밥 (meal), 연세 over 나이 (age). Some formal counterparts are instead suppletive honorifics rather than 한자어 - 주무시다 for 자다 (sleep).

Step 5 - 두음법칙: the initial-sound rule reshapes some roots

A root that starts with ㄹ, or ㄴ before i/y, softens at the start of a word but keeps its original shape inside one. The 한자 is the same; only the 한글 shifts. 女 is 여성 (yeoseong, woman) but 남녀 (namnyeo, men and women); 利 is 이용 (iyong, use) but 편리 (pyeolli, convenience). Do not “fix” 남녀 to *남여.

Forms & patterns

Productive prefixes:

Productive suffixes:

Note on -중: 중 is formally a bound noun and takes a space (회의 중, 근무 중 geunmu jung, at work), though signs and labels routinely write it solid (공사중 gongsajung, under construction).

One noun, three voices with 하다 / 되다 / 시키다:

Register pairs - everyday vs formal:

두음법칙 - same 한자, different 한글:

Examples

Common mistakes

• 회의 중이예요. (Hoeui jungiyeyo.) -> 회의 중이에요. (Hoeui jungieyo.) - 중 ends in a 받침 (ㅇ), so the copula is 이에요; 예요 only follows a vowel. Same allomorph split as 학생이에요 / 친구예요.
• 문제가 곧 해결할 거예요. (Munjega got haegyeolhal geoyeyo.) -> 문제가 곧 해결될 거예요. (Munjega got haegyeoldoel geoyeyo.) - The problem is what gets solved, so it needs the passive 되다 (해결되다), not the active 하다.
• 부모님이 저를 공부했어요. (Bumonimi jeoreul gongbuhaesseoyo.) -> 부모님이 저를 공부시켰어요. (Bumonimi jeoreul gongbusikyeosseoyo.) - To make someone else do it you need the causative 시키다 (공부시키다), not 하다.
• 리용 -> 이용 (iyong); 녀성 -> 여성 (yeoseong). - 두음법칙 softens a word-initial ㄹ / ㄴ. The root is the same 한자, but the spelling and sound shift at the start of a word.
• 이 문제는 사회예요. (I munjeneun sahoeyeyo.) -> 이 문제는 사회적이에요. (I munjeneun sahoejeogieyo.) - To say something is social you need the -적 form; bare 사회 means “society,” the thing, not the quality.

Tips

• Suffixes are reading glasses. Once -화 = “-ization,” -성 = “-ness,” -력 = “power,” -자 = “person” are automatic, brand-new compounds decode themselves: 세계화 (segyehwa, globalization), 창의성 (changuiseong, creativity), 상상력 (sangsangnyeok, imagination), 지원자 (jiwonja, applicant). That is the whole reason this optional lesson pays off.
• -적 is a chameleon in three slots. Attributive 사회적 문제 (a social problem) - or 사회적인 문제 (sahoejeogin munje), because -적 is a noun as well as a bare modifier, and a noun takes the copula’s -인; the bare form is the tighter, more written one. Predicate 사회적이에요 (is social), adverb 사회적으로 (socially). One suffix, three jobs - and the adverb takes -으로, not a bare form.
• 하다 / 되다 / 시키다 is a transitivity dial. Same 한자어 root, three voices: 하다 = do it, 되다 = it happens, 시키다 = make someone do it. When in doubt about who acts, that choice carries it - and it connects straight to passive and causative.
• Don’t over-correct 두음법칙. The same character really is 여성 but 남녀, 이용 but 편리. The initial-sound shift is a spelling rule, not a typo to fix.