gabangeul yeoreo bonikka yeogwoni eobseoyo.

Here, 열어 보니까 means something like when I opened it and checked or when I opened it, I found that...

It comes from:

• 열다 = to open
• -어 보다 = to try doing / to do and see
• -니까 = when / since / because

In this sentence, it does not sound like a deliberate I tried opening it. Instead, it gives the sense of:

• I opened the bag
• then I discovered the result

So the whole middle part feels like I opened the bag and saw that...

In Korean, -아/어 보다 often means to try doing something or to do something and see what happens.

So:

• 열다 = to open
• 열어 보다 = to open and check / open to see

In this sentence, 보다 adds the idea of checking the inside or finding out by opening. It is more natural here than just 가방을 열니까 if the speaker wants to emphasize discovery.

So 열어 보니까 suggests:

• I opened the bag to check
• and then I realized the passport was missing

-니까 connects the first action with the result that follows.

In this sentence, it means when or after doing that, I found that...

So:

• 가방을 열어 보니까 = when I opened the bag and checked
• 여권이 없어요 = the passport isn’t there

A very important nuance is that -니까 often introduces a new realization. The speaker did something, and then discovered something as a result.

That is why this sentence feels very natural for a situation like:

• I opened my bag
• and then I noticed my passport was gone

This is a very common question.

• 가방을 uses -을 because the bag is the object of 열다: you open the bag.
• 여권이 uses -이 because with 있다/없다, the thing that exists or does not exist is usually marked as the subject.

So:

• 가방을 열다 = to open the bag
• 여권이 없다 = the passport is not there / there is no passport

English learners often expect 여권을 없어요, but that is not how Korean works here. 없다 is not used like a normal action verb taking a direct object.

Because 없다 means to not exist, to be absent, or to not have, and the noun before it is usually marked with 이/가.

So:

• 여권이 없어요 = the passport is not there / I don’t have the passport

Using 을/를 would be ungrammatical here.

You can think of 없다 as behaving more like there isn’t X than I not-have X in English grammar terms.

Because 없다 is its own word meaning to not exist / to not have.

So Korean normally says:

• 있어요 = there is / I have
• 없어요 = there isn’t / I don’t have

You generally do not make the negative by saying 안 있어요 in this meaning. The natural opposite of 있어요 is 없어요.

So 여권이 없어요 is the correct and natural form.

Yes, 없어요 is present-style polite speech, but that is normal here.

The sentence describes:

• first, the speaker opened the bag
• then, at that moment, they observed the current state: the passport is not there

So Korean is focusing on the state discovered at that time, not necessarily narrating everything in past tense.

In English, depending on context, you might translate it as:

• When I opened my bag, my passport wasn’t there
• or When I opened my bag, I found that my passport was missing

Korean often uses the present-form 없어요 for the immediate observed situation.

Yes, that is possible, but the nuance changes a little.

• 없어요 focuses on the state as the speaker is reporting it: it’s not there
• 없었어요 places that state more clearly in the past: it wasn’t there

So:

• 여권이 없어요 can feel like an immediate realization
• 여권이 없었어요 can feel more like later narration about what happened

Both can work, but 없어요 sounds very natural if the speaker is describing the discovery more vividly.

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

Here, it is naturally understood that I opened the bag and discovered the passport was missing. So there is no need to say:

• 제가 가방을 열어 보니까...

unless the speaker wants extra emphasis.

This omission is extremely common in Korean and can feel strange to English speakers at first, because English usually requires the subject to be stated.

Yes, you may see both 열어 보니까 and 열어보니까.

This is because 보다 here is an auxiliary verb. In modern Korean writing, the separated form 열어 보니까 is very common and often preferred in careful writing, but the attached form 열어보니까 is also widely seen.

For a learner, the most important point is that both refer to the same structure:

• 열어 보다
• 열어 보니까 / 열어보니까

가방을 여니까 simply means when I opened the bag.

가방을 열어 보니까 adds a stronger feeling of:

• opening it
• checking inside
• discovering the result

So the version with -어 보다 is especially natural when the speaker is talking about finding something out by doing the action.

Compare:

• 가방을 여니까... = when I opened the bag...
• 가방을 열어 보니까... = when I opened the bag and checked, I found that...

Yes, very natural.

A Korean speaker could say this in a real situation such as:

• at the airport
• while packing
• after checking a bag and realizing something important is missing

It sounds conversational and normal. The -아/어 보니까 pattern is especially common when explaining how you discovered something.

Good question. Both are possible, but the nuance is different.

• 여권이 없어요 simply states the fact: the passport is missing
• 여권은 없어요 adds contrast or emphasis, like as for the passport, it’s not there or the passport, at least, is missing

For example, 여권은 없어요 might sound natural if:

• other things are in the bag, but not the passport
• the speaker is contrasting the passport with something else

In this sentence, 여권이 없어요 is the most neutral and natural choice.

없어요 is pronounced roughly like 업써요.

This happens because of Korean sound changes:

• 없
  • 어요
• the pronunciation becomes 업써요

So even though it is written 없어요, you will usually hear something close to 업써요.

Also, 열어 is pronounced roughly like 여러, so 열어 보니까 sounds close to 여러 보니까 in natural speech.