Adjectives before nouns: 큰 가방, 좋은 친구

In front of a noun, the adjective ends in ㄴ

가방이 커요 — the bag is big. 큰 가방 — a big bag. 예뻐요 becomes 예쁜 옷, pretty clothes. 바빠요 becomes 바쁜 친구, a busy friend.

The order is the English one: describing word first, noun second. But the adjective cannot keep its 요 ending there. That ending closes a sentence. In front of a noun the adjective takes a different shape, and in all three examples it ends in ㄴ.

Vowel stem + ㄴ, consonant stem + 은

Start from the stem: the dictionary form minus 다. 크 + ㄴ = 큰. 비싸 + ㄴ = 비싼. A stem ending in a vowel takes ㄴ underneath. A stem ending in a consonant has no room, so it takes 은: 작은 방, 좋은 친구, 많은 사람들.

Textbooks write this ending -(으)ㄴ and call the result the noun-modifying form. Build it from the stem, not from the 해요 form: 예뻐요 gives 예쁜, with the ㅡ of 예쁘다 back in place.

좋은 sounds like [조은], 많은 like [마는], 작은 like [자근]. 사람들 is 사람 with the plural marker 들.

있다 and 없다 words take 는

맛있어요 → 맛있는 음식, tasty food. 재미있어요 → 재미있는 영화, a fun film. 재미없어요 → 재미없는 드라마, a boring drama.

These stems end in a consonant, so 은 would be the expected choice. But adjectives built on 있다 or 없다 are the exception: they take 는. There are only a handful and you know most of them already. The new noun is 음식, food.

맛있는 is pronounced [마신는], 재미있는 [재미인는], 재미없는 [재미엄는].

하다 adjectives end in 한

따뜻해요 is “is warm”, dictionary form 따뜻하다. 조용해요 is “is quiet”, dictionary form 조용하다. Their stems end in 하, a vowel, so ㄴ goes underneath: 따뜻한 날씨, warm weather; 조용한 영화관, a quiet cinema.

Every 하다 adjective works this way. Two new nouns come with them: 날씨 (weather) and 영화관 (cinema), which is 영화 plus a syllable meaning “hall”.

따뜻한 is pronounced [따뜨탄].

Short and long: 짧은, 긴

치마가 짧아요 — the skirt is short. 짧은 치마 — a short skirt. The stem 짧 ends in a consonant and takes 은, as the rule says.

바지가 길어요 — the trousers are long. 긴 바지 — long trousers. Here the stem 길 loses its ㄹ when ㄴ arrives. Learn 긴 as a ready-made word for now.

짧은 is pronounced [짤븐].

새 never changes

새 가방 — a new bag. 새 휴대폰을 샀어요 — I bought a new phone.

새 means “new”, but it is not an adjective like 큰 or 좋은. It has no stem, no 다 form and no 해요 form. It exists only in this position, as a separate word directly before a noun, and it never takes an ending. So there is nothing to build: just put 새 in front.