i gabangeun keoseo mugeowoyo.

은/는 marks the topic (what you’re talking about in general).
So 이 가방은… means “As for this bag…” and then you comment on it.

이 가방이… would mark the subject and is more typical when you’re identifying which bag (or emphasizing that this bag is the one causing the situation). For example:

• 이 가방이 커서 무거워요. = “This bag is big, so it’s heavy.” (more straightforward subject marking)
• 이 가방은 커서 무거워요. = “This bag, (it) is big so it’s heavy.” (topic/contrast-friendly)

커서 is the adjective (descriptive verb) 크다 (to be big) + the connector -아서/어서.

• 크다 → stem 크-
• -어서 attaches, but 크 + 어서 contracts to 커서

So 커서 means because it’s big / being big, (so)….

-아서/어서 can express: 1) Cause/Reason: “because / so” 2) Sequence: “and then (as a result)”

In 이 가방은 커서 무거워요, it’s clearly cause: being big explains why it’s heavy.

A more “sequence” feel often appears with actions:

• 집에 가서 쉬었어요. = “I went home and then rested.”

With adjectives like 크다 → 커서, it commonly reads as cause.

They describe different properties with a cause relationship:

• 커서 = “because it’s big”
• 무거워요 = “it’s heavy”

The structure is basically: (Reason) + (result).
You’re not saying “big and heavy” equally; you’re saying it’s heavy because it’s big.

If you just wanted to list two traits, you might use -고:

• 이 가방은 크고 무거워요. = “This bag is big and heavy.” (no “because”)

Yes, and the meaning is similar:

• 이 가방은 커서 무거워요.
• 이 가방은 크니까 무거워요.

Common nuance:

• -아서/어서 often sounds like a straightforward, natural cause.
• -(으)니까 can sound a bit more like giving a reason/explanation (and can be used when the speaker is presenting a reason more explicitly).

Both are natural here; 커서 is very common and smooth.

Because 무거워요 is the main clause ending (the final statement).
-아서/어서 (like 무거워서) is usually used to connect to something that comes after it.

You can end with …무거워서요 in conversation, but it typically implies something is omitted:

• 이 가방은 커서 무거워서요. = “It’s big, so it’s heavy, so…” (implying something like “I can’t carry it” / “I don’t want it”)

For a complete standalone statement, 무거워요 is the clean ending.

무거워요 is polite informal (해요체), very common in daily speech.

Other options:

• 무거워. (casual, to friends)
• 무겁습니다. (formal, polite)
• 무거워요? (polite question: “Is it heavy?”)

Same pattern applies to 크다 if it were final:

• 커요 / 커. / 큽니다

가방 is the noun “bag,” and particles attach depending on its role:

• 이 가방은 (topic)
• 이 가방이 (subject)
• 이 가방을 (object, e.g., “I bought this bag” → 이 가방을 샀어요)

In your sentence, the bag is what you’re talking about (topic), so 은 fits well.

이 means this (near the speaker).
Demonstratives:

• 이 가방 = this bag (near me)
• 그 가방 = that bag (near you / or previously mentioned)
• 저 가방 = that bag over there (far from both)

So the sentence could be:

• 저 가방은 커서 무거워요. = “That bag over there is big, so it’s heavy.”

Dictionary form: 크다 (to be big)

Pattern: adjective/verb stem + -아서/어서
Examples:

• 작다 (small) → 작아서 (because it’s small)
• 비싸다 (expensive) → 비싸서
• 무겁다 (heavy) → 무거워서 (note: 무겁- + 어서 → 무거워서)

So you can make similar sentences like:

• 이 신발은 비싸서 못 사요. = “These shoes are expensive, so I can’t buy them.”

Yes: it’s a contraction.

• Underlying form: 크 + 어서
• Spoken/written form: 커서

This kind of change is common when ㅡ meets 어.

Yes. They usually go right before the adjective they modify:

• 이 가방은 너무 커서 무거워요. = “This bag is too big, so it’s heavy.”
• 이 가방은 정말 커서 무거워요. = “This bag is really big, so it’s heavy.”

You can also intensify the result:

• 이 가방은 커서 정말 무거워요. = “It’s big, so it’s really heavy.”