kuponi isseumyeon i sinbareul deo ssage sal su isseoyo.

Because 쿠폰 is the thing that exists / is available, not the thing being bought.

In 쿠폰이 있으면, the verb is 있다 (to exist, to have). With 있다, the thing that exists usually takes 이/가.

• 쿠폰이 있다 = There is a coupon / You have a coupon

So here, 쿠폰이 있으면 means if there is a coupon or if you have a coupon.

If you used 쿠폰을, it would sound wrong with 있다.

-으면 / -면 makes an if/when clause.

• 있다 → 있으면 = if there is / if you have
• 가다 → 가면 = if/when (someone) goes
• 먹다 → 먹으면 = if/when (someone) eats

So:

• 쿠폰이 있으면 = if you have a coupon

This pattern is very common for conditions.

A quick rule:

• after stems ending in a consonant: -으면
• after stems ending in a vowel: -면

Since 있다 has the stem 있-, it becomes 있으면.

Because 싸게 is the adverb form, and it describes how you buy the shoes.

• 싸다 = to be cheap
• 싸게 = cheaply

In this sentence, the word modifies 살 수 있어요 (can buy), so you need the adverb form:

• 더 싸게 살 수 있어요 = can buy (them) more cheaply

Compare:

• 싼 신발 = cheap shoes (싼 modifies a noun)
• 신발이 싸요 = the shoes are cheap
• 싸게 사요 = buy cheaply

더 means more.

So:

• 싸게 = cheaply
• 더 싸게 = more cheaply

In natural English, this often becomes:

• at a lower price
• more cheaply
• cheaper

So the sentence means you can buy these shoes for less money than otherwise if you have a coupon.

살 수 있어요 is the can / be able to pattern.

It is built like this:

• 사다 = to buy
• verb stem: 사-
• -(으)ㄹ 수 있다 = can / be able to
• 사 + ㄹ 수 있다 → 살 수 있다

Then in polite style:

• 살 수 있어요 = can buy

So:

• 이 신발을 살 수 있어요 = you can buy these shoes
• 더 싸게 살 수 있어요 = you can buy them more cheaply

This pattern is used with many verbs:

• 먹을 수 있어요 = can eat
• 갈 수 있어요 = can go
• 볼 수 있어요 = can see/watch

Because 신발 is the object of 사다 (to buy), so it takes 을/를.

• 이 신발을 사다 = to buy these shoes

Here:

• 이 = this / these
• 신발 = shoes
• 을 = object marker

So 이 신발을 means these shoes as the thing being bought.

A small note: although 신발 can refer to footwear in general, in context it often translates naturally as these shoes.

Good question. In Korean, 신발 is often treated like a general noun meaning shoes/footwear, and number is often not marked clearly.

So:

• 이 신발 can mean this shoe
• but in many real situations it can also mean these shoes

Korean often leaves singular/plural to context.

If Korean wants to be extra explicit about plural, it might use 신발들, but with objects like shoes that is often unnecessary or unnatural.

So the English translation may use these shoes even though the Korean literally looks like this shoe.

Yes. Korean often leaves out the subject when it is obvious from context.

The sentence does not explicitly say you, but it is understood:

• (당신은) 쿠폰이 있으면 이 신발을 더 싸게 살 수 있어요.
• If you have a coupon, you can buy these shoes more cheaply.

In Korean, including 당신은 here would often sound unnatural unless you specifically need contrast or emphasis.

So omission of you is normal and natural.

This is the polite informal style, often called 해요체.

• 있어요
• 살 수 있어요

This style is very common in everyday conversation, shops, customer service, and polite speech in general.

Compare:

• 있다 / 살 수 있다 = plain dictionary style
• 있어요 / 살 수 있어요 = polite everyday style
• 있습니다 / 살 수 있습니다 = more formal and stiff

So this sentence sounds polite and natural, like something a store clerk might say.

Yes. -으면 / -면 can mean if or when, depending on context.

• 쿠폰이 있으면 can mean if you have a coupon
• in some contexts, it can feel like when you have a coupon

In this sentence, English usually prefers if, because it is talking about a condition for getting a discount.

So if you have a coupon is the best translation here.

They are related, but not exactly the same.

• 더 싸게 살 수 있어요 = you can buy it more cheaply
• 할인받을 수 있어요 = you can get a discount

The first focuses on the result: the purchase price is lower. The second focuses on the discount itself.

In a shopping situation, both are natural, but the nuance is slightly different.

For example:

• 쿠폰이 있으면 이 신발을 더 싸게 살 수 있어요.
• 쿠폰이 있으면 할인받을 수 있어요.

Both are fine, but the original sentence directly emphasizes buying the shoes at a cheaper price.

Yes, to some extent. Korean word order is flexible as long as the grammar markers stay clear.

Original:

• 쿠폰이 있으면 이 신발을 더 싸게 살 수 있어요.

You could also say:

• 이 신발을 쿠폰이 있으면 더 싸게 살 수 있어요.

This is still understandable, but the original sounds more natural because the condition 쿠폰이 있으면 comes first.

In Korean, the main verb usually comes at the end, but other parts can move around for emphasis or flow.

In careful pronunciation, it is something like:

• 살 수 있어요

But in natural speech, it often sounds smoother, roughly like:

• 살 쑤 이써요

This is because Korean pronunciation changes happen between words:

• 수 after 살 may sound more tense
• 있어요 is commonly heard close to 이써요

You do not need to force this too much at first, but it is good to recognize it when listening.

Yes, you can.

• 싸게 살 수 있어요 = can buy it cheaply
• 더 싸게 살 수 있어요 = can buy it more cheaply

Adding 더 makes it sound more comparative: cheaper than the normal price, or cheaper than without the coupon.

Without 더, the sentence is still grammatical, but it may sound slightly less specific about the comparison.

In this coupon context, 더 is very natural because a coupon usually means a lower price than usual.