Learn Hardcore Korean: gabangi mugeowoseo pari apayo. - My arm hurts because the bag is heavy.

The particle 이 marks 가방 as the subject of the clause. In Korean, subjects are marked by 이 (after consonants) or 가 (after vowels). Here, 가방 ends in a consonant, so it takes 이.

Why is 저는 (I) omitted before 가방이?

Korean often drops pronouns when the context is clear. Since it’s obvious you are talking about your own bag and your own arms, you don’t need to say 저는. Omitting it makes the sentence more natural and concise.

How do we get 무거워서 from the dictionary form 무겁다?

Remove the ending -다 → 무겁
Attach the connective -아서/어서. Since the verb stem 무겁 ends in a consonant, you use -어서 → 무거워서
This form means “because it is heavy” or “so it is heavy,” linking cause and effect.

Why use -아서/어서 here instead of -니까 or -기 때문에?

-아서/어서 is a colloquial, smooth connector for cause-and-effect, common in spoken Korean.
-니까 is more formal and often used when asking a follow-up or giving instructions: 가방이 무거우니까…
-기 때문에 is also causal but more formal/written: 가방이 무겁기 때문에…
All three are correct but differ in nuance and register.

Why is 팔 marked with 이 in 팔이 아파요?

Just like 가방이, 팔이 marks 팔 (arm) as the subject of the verb 아프다 (to hurt). The structure is [subject] + 이/가 + 아프다 to express that a body part hurts.

What exactly does 아파요 mean, and why is it present tense?

아파요 is the polite present tense of 아프다, meaning “(it) hurts” or “(I) am in pain.” Present tense is used because you currently feel pain in your arm. If you felt pain in the past, you’d say 아팠어요.

Could you say “My arms hurt” as 팔들이 아파요 or use a plural marker?

You generally don’t need a plural marker 들 for body parts when it’s obvious or natural. 팔이 아파요 can mean “my arm hurts” or “my arms hurt,” depending on context. Adding 들 (팔들이) isn’t wrong but feels redundant.

Is there any nuance to using a connective ending like -어서 rather than two separate sentences?

Yes. By connecting with -어서, you show a direct cause-and-effect relationship in one smooth sentence: “Because the bag is heavy, my arm hurts.” Splitting into two sentences (가방이 무거워요. 팔이 아파요.) makes them sound more like unrelated statements.