Learn Hardcore Korean: baekhwajeomeun sijangboda deo bissayo. - The department store is more expensive than the market.

In Korean, 은/는 is the topic marker, while 이/가 marks the subject and 을/를 marks the object. Here 백화점은 sets “department store” as the topic (“As for department stores…”), showing what you’re talking about. Using 이/가 would simply state the subject, and 을/를 doesn’t fit because you’re not acting on the department store, you’re describing it.

What does 보다 mean in 시장보다?

보다 means “than” in comparisons. It attaches to the noun you’re comparing to, so 시장보다 literally means “than the market.”

What is the function of 더 in this sentence?

더 means “more.” In comparatives you can say either 시장보다 비싸요 or 시장보다 더 비싸요. Adding 더 emphasizes “even more” expensive.

Why is the adjective 비싸요 at the end?

Korean adjectives (descriptive verbs) always come at the end of a sentence as the predicate. 비싸요 is the polite present form of 비싸다 (“to be expensive”).

Why don’t we use an object marker with 시장?

Because in a comparison you use 보다 (“than”) instead of the object marker 을/를. 시장보다 indicates “compared to the market.”

Can we drop 은 and just say 백화점 시장보다 더 비싸요?

You might hear that in very casual speech, but it sounds abrupt or incomplete. Using 백화점은 clearly introduces the topic and makes the sentence flow naturally.

Could we use 이 instead of 은 and say 백화점이 시장보다 더 비싸요?

Yes. 백화점이 marks “department store” as the grammatical subject rather than the topic. The sentence still means “department stores are more expensive than markets,” but the nuance shifts slightly (more neutral statement vs. topic contrast).

Why is the ending -아요 in 비싸요?

-아요/-어요 is the polite informal speech level in Korean. Since 비싸다 ends in the vowel ㅏ, you attach -아요 to get 비싸요, which is polite yet conversational.