Korean Adjectives Are Verbs (형용사 = Descriptive Verbs)

If you internalize one thing about Korean adjectives, make it this: a Korean adjective is a verb. What English calls an adjective — "good," "pretty," "big" — Korean encodes as a 형용사, a descriptive (or stative) verb that conjugates exactly like an action verb and stands as a complete predicate all by itself. 좋다 is not the adjective "good" waiting for a separate "is." 좋다 already means "to be good." So 날씨가 좋다 is a whole sentence — "the weather is good" — with no copula anywhere in it. Get this one idea, and the entire Adjectives group stops being a list of exceptions and becomes a single, predictable system.

The English model you have to unlearn

English builds description in two pieces: an adjective ("good") plus the verb "to be" ("the weather is good"). The adjective carries meaning; the verb to be does the grammatical work of predicating — taking tense, agreement, and so on.

Korean fuses both jobs into one word. The descriptive verb is the predicate; there is no "to be" to add.

There is no word for "is" in that sentence. 좋아요 alone means "is good / is nice." The whole "the weather IS good" idea lives inside the single verb 좋다, conjugated politely to 좋아요. English needs two words; Korean needs one, because its adjective is already a verb.

Three anchors that predicate on their own

Watch three everyday descriptive verbs stand as complete predicates with nothing glued on:

예쁘다 → 예뻐요 ("is pretty"), 크다 → 커요 ("is big"), 조용하다 → 조용해요 ("is quiet"). Each is the predicate; each takes the polite ending directly. Nowhere do you add 이다 (the copula) or any "be" verb — the descriptive verb has already done that work.

They conjugate exactly like action verbs

Because a 형용사 is a verb, it wears the same endings as an action verb. Put the action verb 먹다 ("to eat") next to the descriptive verb 좋다 ("to be good") and the parallel is exact:

Same 아/어요, same past -았/었-, same formal 습니다, same connective 아서. A Korean adjective is not a word that needs conjugating help from a copula — it conjugates itself, on the identical machinery as 먹다 and 가다.

That past tense, 나빴어요, comes straight off 나쁘다 ("to be bad") with the ordinary verb past -았어요 — no "was" added, because the descriptive verb already means "to be bad."

The one place adjectives and action verbs split

Descriptive verbs behave like action verbs almost everywhere — with one systematic exception, and it's the spine of this whole group: the present attributive ending (the form a verb takes to modify a following noun).

• Action verbs use -는: 먹는 사람 ("a person who eats"), 가는 길 ("the road one is going on").
• Descriptive verbs use -(으)ㄴ: 좋은 사람 ("a good person / a person who is good"), 예쁜 꽃 ("a pretty flower").

좋은 사람 (adjective + 은) versus 먹는 사람 (verb + 는): that single divergence — 은 for descriptive verbs, 는 for action verbs — is the one place where "is it an adjective or an action verb?" actually changes the ending you pick. Everywhere else they march in step. This is important enough to have its own page: 은 vs 는: adjective vs verb attributive.

(Interestingly, the copula 이다 sides with the adjectives here, taking 인 — 학생인 친구 — which is more evidence that 이다 itself conjugates like a descriptive verb.)

"To be good" vs "to like": don't smuggle in an object

One consequence trips up English speakers immediately. Since 좋다 means "to be good/likeable," it is intransitive — the thing you like is the subject, marked with 이/가, not an object:

If you want "to like" as a transitive action with a direct object, that's a different verb — the action verb 좋아하다, which takes 을/를: 커피를 좋아해요. The two are genuinely separate words, and choosing between them is its own skill — see 좋다 vs 좋아하다. The takeaway for now: 좋다 is a descriptive verb ("is good/nice/likeable"), and like all descriptive verbs it describes a subject, it doesn't act on an object.

Common Mistakes

1. Gluing 이다 onto an adjective. The single most common English-speaker error, straight from the "adjective + to be" habit. The adjective is the predicate; there is no "be" to add.

2. Using the attributive form as a predicate + copula. 예쁜 is the modifier form; it can't take 이에요 to make a sentence.

3. Turning a 하다-adjective into a noun + 이다. 피곤하다 ("to be tired") is one word, a descriptive verb — not 피곤 ("fatigue") plus a copula.

4. Giving a descriptive verb the action-verb attributive -는. Adjectives take -(으)ㄴ.

Key Takeaways

• A Korean adjective is a descriptive verb (형용사): 좋다 = "to be good," not "good" + a separate "is."
• It predicates on its own and conjugates like an action verb — same 아/어요, past -았/었-, formal 습니다, connective 아서 (좋아요 / 먹어요, 좋았어요 / 먹었어요).
• Never add 이다 to an adjective (×날씨가 좋이에요) — the descriptive verb already contains the "be."
• The one systematic split from action verbs is the present attributive: adjectives take -(으)ㄴ (좋은 사람), action verbs take -는 (먹는 사람). That divide is the spine of this group.
• 좋다 ("to be likeable") is intransitive and takes a 이/가 subject; the transitive "to like" is the separate action verb 좋아하다 (을/를).