changmuneul yeolmyeon gongwoni boyeoyo.

-면 is a conditional ending. It means if, when, or once, depending on context.

So 열면 comes from 열다 (to open) + -면, giving the idea:

• if you open
• when you open
• once you open

In this sentence, it often feels very natural as when/if you open the window, the park is visible.

창문을 uses the object particle -을/를 because 창문 is the thing being opened.

• 창문 = window
• 열다 = to open
• 창문을 열다 = to open the window

So the window is the object of the verb 열다.

Because with 보이다 / 보여요, the thing that is seen is usually marked with the subject particle -이/가, not the object particle -을/를.

So:

• 공원이 보여요 = the park is visible / the park can be seen

Here, 공원 is not something you are actively looking at as a direct object in the same way as with 보다. Instead, it is the thing that appears in view.

That is why 공원이 보여요 sounds natural.

This is a very common question.

• 봐요 comes from 보다 = to see / to look at
• 보여요 comes from 보이다 = to be seen / to be visible

Compare:

• 공원을 봐요 = I look at the park / I see the park
• 공원이 보여요 = the park is visible / the park comes into view

In this sentence, 보여요 is better because the idea is not really I intentionally look at the park, but rather when the window is opened, the park becomes visible.

It is often easiest for learners to understand it that way, yes.

보이다 is related to 보다, but it expresses the idea that something is seen, becomes visible, or appears to the eye.

So in practice, 공원이 보여요 works a lot like:

• the park is seen
• the park can be seen
• the park is visible

It does not always behave exactly like a simple English passive, but thinking of it as be visible / be seen is very helpful.

Korean often leaves out the subject when it is obvious or unimportant.

So 창문을 열면 could mean:

• if you open the window
• when we open the window
• when one opens the window

The sentence focuses on the situation, not on who does the action. This is very normal in Korean.

If needed, you could add a subject, but in many everyday situations it is unnecessary.

It can suggest either one, and Korean often leaves that open.

In this sentence, the most natural feeling is usually:

• when you open the window, the park is visible or
• if you open the window, you can see the park

The exact English choice depends on context:

• If you are describing a general fact, when may sound more natural.
• If you are talking about a possible action, if may sound more natural.

Korean -면 comfortably covers both ideas.

That sentence is grammatically possible in some contexts, but it means something different.

• 공원을 봐요 = I look at the park / I see the park
• 공원이 보여요 = the park is visible

With 창문을 열면 공원을 봐요, the focus is on a person actively seeing or looking at the park.

With 창문을 열면 공원이 보여요, the focus is on what becomes visible after opening the window.

For this kind of description, 보여요 is the more natural choice.

보여요 is in the polite informal style, often called -아요/어요 style.

It is polite and very common in everyday conversation.

Related forms:

• 보여 = casual
• 보여요 = polite everyday speech
• 보입니다 = more formal polite speech

So this sentence sounds natural and standard in normal conversation.

Yes. Very naturally.

창문을 열면 공원이 보여요 can describe a regular situation or general fact, such as:

• from this room, opening the window lets you see the park
• whenever the window is opened, the park is visible

Korean -면 is often used for this kind of general condition.

Sometimes, yes.

보여요 can simply mean is visible, but depending on context it can also suggest that something comes into sight or appears before your eyes.

So here, after opening the window, the park is not just something you deliberately look at; it is something that naturally comes into view.

That nuance is one reason 보여요 fits so well in this sentence.