In short

To turn a whole clause into an adjective that sits in front of a noun, attach a modifier ending to the verb stem and place the clause before the noun: 먹는 사람 (meongneun saram, the person who eats), 먹은 사람 (meogeun saram, the person who ate), 먹을 사람 (meogeul saram, the person who will eat). Action verbs choose the ending by tense (-는 / -(으)ㄴ / -(으)ㄹ), describing words use -(으)ㄴ for the plain present, and a handful of nouns (것, 수, 때 …) live at the end of such a clause - always written with a space in front.

The rule

Step 1 - A modifier clause comes BEFORE its noun

Korean has no “who/which/that”. Instead the whole clause is turned into a modifier and set directly in front of the noun it describes, with the modifier ending doing the linking work: Clause + modifier ending + Noun. English says the book that I read; Korean says 읽은 책 (ilgeun chaek), literally read book. There is nothing between the ending and the noun.

Step 2 - Action verbs pick the ending by tense

For a 동사 (action verb) the ending encodes when the action happens relative to the main sentence:

• Present / ongoing -는: 먹는 (meongneun, that eats / is eating)
• Past / completed -(으)ㄴ: 먹은 (meogeun, that ate)
• Prospective / irrealis -(으)ㄹ: 먹을 (meogeul, that will eat / to eat)

-는 is the same after every action verb (vowel or consonant stem): 가는 (ganeun), 먹는 (meongneun). -(으)ㄴ and -(으)ㄹ are the familiar -(으)- endings from lesson 17: a bare ㄴ/ㄹ after a vowel stem, 은/을 after a 받침.

Step 3 - Describing words use -(으)ㄴ for the plain present

A 형용사 (descriptive verb) does not take -는. Its everyday attributive form is -(으)ㄴ: 예쁜 (yeppeun, pretty), 좋은 (joeun, good), 큰 (keun, big), 작은 (jageun, small), 많은 (maneun, many). Watch the overlap: the very ending that means past on a verb (먹은) means present on an adjective (작은). The word class tells you which reading applies.

Step 4 - 있다/없다 behave like verbs; 이다 uses -인

Anything built on 있다/없다 takes the verb-style -는, even though it feels adjective-like: 맛있는 (masinneun, tasty), 재미있는 (jaemiinneun, fun), 재미없는 (jaemieomneun, boring), 없는 (eomneun, that has none). The copula 이다 (lesson 2) makes its present modifier with -ㄴ: 학생인 (haksaengin, who is a student).

Step 5 - Irregular stems change first, then take the ending

The -(으)ㄴ and -(으)ㄹ modifiers are more -(으)- endings, so the irregular classes fire exactly as in lesson 17; -는 is plain consonant-initial, so a ㅂ, ㄷ or ㅅ stem is written in front of it exactly as in the dictionary - 돕다 -> 돕는, 듣다 -> 듣는, 짓다 -> 짓는 - and only a ㄹ-stem reacts. A ㄹ-stem drops its ㄹ before -는 and before -(으)ㄴ: 살다 -> 사는 (saneun, present), 산 (san, past), 살 (sal, prospective); 만들다 -> 만드는, 만든 (mandeuneun, mandeun); 알다 -> 아는 (aneun). ㅂ: 덥다 -> 더운 (deoun, hot). ㄷ: 듣다 -> 들은 (deureun, that heard). ㅅ: 짓다 -> 지은 (jieun, that built).

Step 6 - Bound nouns: real nouns that cannot stand alone

Some nouns habitually sit at the end of a modifier clause, and they always take a space in front. 것, 수, 적, 지, 중 are true 의존명사 (bound nouns) and cannot stand alone at all; 때, 후, 동안 are ordinary nouns that can also follow a plain noun (방학 때, 식사 후) - either way the space is required. Learn them as vocabulary: 것/거 (thing, the act/fact), 수 (possibility), 때 (time/when), 후 (after), 적 (a past occasion), 지 (elapsed time since), 동안 (during/while), 중 (in the middle of). Note the spacing in 할 수 있어요 (hal su isseoyo, can do) and 갈 때 (gal ttae, when going) - the full spacing rules are in lesson 46.

Forms & patterns

The core allomorph table - modifier endings by stem type:

Which ending each word class takes:

Bound nouns - the modifier they usually follow, and the spacing:

Examples

Common mistakes

• 좋는 사람 (jonneun saram) -> 좋은 사람 (joeun saram) - 좋다 is a describing word, so its present modifier is -(으)ㄴ, not the verb-style -는. A good person.
• 지금 먹은 사람 (jigeum meogeun saram) -> 지금 먹는 사람 (jigeum meongneun saram) - on an action verb -(으)ㄴ is past; for the ongoing present you need -는. 지금 (now) forces the present reading.
• 맛있은 음식 (masiseun eumsik) -> 맛있는 음식 (masinneun eumsik) - anything on 있다/없다 modifies like a verb and takes -는, never -(으)ㄴ. Tasty food.
• 살는 집 (salleun jip) -> 사는 집 (saneun jip) - a ㄹ-stem drops its ㄹ before the ㄴ of -는. The house one lives in.
• 할수있어요 (halsuisseoyo) -> 할 수 있어요 (hal su isseoyo) - 수 is a bound noun and needs a space on each side; run it together and the phrase is misspelled.

Tips

• One-second class check. Action verb present = -는 (먹는); describing word present = -(으)ㄴ (좋은). The same -(으)ㄴ that reads as PAST on a verb reads as PRESENT on an adjective - the word class decides.
• The verb timeline runs ㄹ -> 는 -> ㄴ. Prospective 먹을, present 먹는, past 먹은. Say the three in a row for any verb and the shapes stick.
• 있다/없다 are honorary verbs. They feel like adjectives but always take -는: 맛있는, 재미있는, 재미없는, 없는. Same for every 있다/없다 compound.
• If a modifier can sit in front of it, it takes a space. 할 수, 갈 때, 먹은 후, 온 지 - bound or ordinary nouns, all spaced. (Full spacing rules live in lesson 46.)