Descriptive verbs — 좋다, 예쁘다, 크다
In Korean, what English calls an 'adjective' is actually a descriptive verb. 좋다 ('to be good') ends in -다 just like 가다 ('to go'), and it conjugates the same way: drop -다, add -아요/-어요. So 좋다 → 좋아요 ('it's good'), 예쁘다 → 예뻐요 ('it's pretty'), 크다 → 커요 ('it's big'). You don't add a copula like 이에요 — the descriptive verb IS the predicate. This is one of the most beginner-confusing parts of Korean, and one of the most freeing once it clicks.
No 'is' before an adjective
English says 'the book is good' — two words for the predicate. Korean says 책이 좋아요 — the verb 좋아요 does both jobs. Don't try to insert 이에요 ('is'); that's only for noun-equals-noun sentences (lesson 2). When the predicate describes a quality, the descriptive verb stands alone. 사과가 커요 = 'the apple is big'. 친구가 좋아요 = 'the friend is good / I like the friend'.
Same conjugation as action verbs
All the lesson-8 rules apply. 좋다 → stem 좋- (vowel ㅗ) → 좋아요. 작다 ('to be small') → 작- (vowel ㅏ) → 작아요. 있다's relative 재미있다 ('to be fun') → 재미있어요. The same vowel-harmony test (ㅏ/ㅗ → -아요, else -어요) drives both action and descriptive verbs.
Vowel-stem contractions hit again
예쁘다 ('to be pretty') has the irregular 으-stem pattern: 예쁘- + -어요 drops the ㅡ and becomes 예뻐요 (ye-ppeo-yo). 크다 ('to be big') → 크- + -어요 → drops ㅡ → 커요. 바쁘다 ('to be busy') → 바빠요 (the ㅡ drops, then ㅏ wins because of the previous syllable's vowel). The pattern: stems ending in ㅡ drop the ㅡ before -아요/-어요, and the ending's vowel takes over. Don't memorize the rule cold — meet a few examples and the pattern becomes obvious.
Modifying a noun: stem + -ㄴ/-은
To use a descriptive verb in front of a noun (English 'a good book'), you don't keep the polite ending. Instead you swap to a special modifier form: 좋다 → 좋은 책 ('a good book'), 예쁘다 → 예쁜 사람 ('a pretty person'), 크다 → 큰 집 ('a big house'). The rule: -은 after a consonant-ending stem, -ㄴ after a vowel-ending stem. We're not drilling the modifier form yet — just notice that descriptive verbs reshape, and that's why 예쁜 and 예뻐요 look related but different.
I like it = it is good (to me)
Korean often expresses 'I like X' as 'X is good': 사과가 좋아요 = 'I like apples' / 'apples are good'. The thing being liked takes the subject particle, and the verb is 좋다 in its polite form. There's a separate verb 좋아하다 ('to like') that's grammatically transitive and takes an object — but at A1 you'll lean on 좋다 for liking. Both are heard constantly.
