Quầy ở trong bưu điện.

Quầy usually means a counter, service desk, stall, or booth, depending on context.

In Quầy ở trong bưu điện, it most naturally means a counter or service counter inside the post office.

For example:

• quầy bán vé = ticket counter
• quầy lễ tân = reception desk
• quầy hàng = stall / sales counter

So the exact English word can change a little depending on what kind of quầy it is.

Vietnamese often does not use a separate verb exactly like English to be in the same way.

In this sentence, ở does the job of expressing location, so Quầy ở trong bưu điện literally works like:

• quầy = counter
• ở = be located at / in
• trong bưu điện = inside the post office

So ở is the key word showing where something is.

They are related, but they do different jobs.

• ở marks location: to be at / to be located at
• trong means inside

So:

• ở trong = to be inside / to be located inside

In this sentence:

• Quầy ở trong bưu điện = The counter is inside the post office.

If you removed trong and said Quầy ở bưu điện, that would mean something more like:

• The counter is at the post office

That is less specifically inside.

Not usually if you want a full sentence meaning The counter is in the post office.

Quầy trong bưu điện sounds more like a noun phrase:

• the counter in the post office

It feels incomplete as a full statement in many contexts.

To make it a clear sentence about location, ở is very helpful:

• Quầy ở trong bưu điện.

Bưu điện means post office.

It is a fixed compound noun:

• bưu relates to mail/post
• điện historically relates to telegraph/communications in this kind of compound

You should learn bưu điện as a set phrase meaning post office.

Vietnamese word order here is quite straightforward:

• Quầy = subject
• ở = location verb
• trong bưu điện = location phrase

So the pattern is:

thing + ở + place

Examples:

• Tôi ở nhà. = I am at home.
• Sách ở trên bàn. = The book is on the table.
• Quầy ở trong bưu điện. = The counter is in the post office.

So in this sentence, the order is very natural.

Vietnamese usually does not use articles like a, an, and the the way English does.

Whether quầy means a counter or the counter, and whether bưu điện means a post office or the post office, depends on context.

So:

• Quầy ở trong bưu điện could be understood as The counter is in the post office
• In another context, it might be A counter is in the post office, though that is less likely in natural English

Vietnamese often leaves this kind of definiteness unstated unless it needs to be made clear.

Not in this sentence.

Vietnamese classifiers are often used when specifying or counting nouns, but bare nouns are also very common.

For example:

• một cái quầy = one counter
• cái quầy đó = that counter

But in a simple sentence like:

• Quầy ở trong bưu điện

using just quầy is normal, especially when the noun is already understood from context or used in a general way.

Yes, often it is.

Ở trong clearly emphasizes physical location inside something.

Compare:

• ở trong bưu điện = located inside the post office
• trong bưu điện = in the post office / inside the post office, but without the same clear verbal role by itself

So ở trong is a very common and natural way to say that something is physically inside a place.

A rough guide:

• quầy sounds somewhat like kway, but with a falling tone

A few pronunciation notes:

• qu in Vietnamese is pronounced like kw
• ầy has a vowel somewhat like the ay in day, but not exactly the same
• the tone on quầy is the huyền tone, a low falling tone

So it is approximately:

• quầy ≈ kwầy with a falling tone

A rough guide:

• bưu sounds a bit like byoo
• điện sounds somewhat like dee-en with a dipping/heavy tone

A few notes:

• đ is like a regular English d
• ưu is not exactly an English vowel combination, so it takes practice
• điện has the nặng tone, which is short and heavy/glottalized in many accents

So approximately:

• bưu điện ≈ byoo dee-en, with Vietnamese tones added

Yes, it is natural and grammatical.

It is a simple, clear location sentence. A Vietnamese speaker might say it when answering a question like:

• Quầy ở đâu? = Where is the counter?

A slightly different but also natural version is:

• Quầy nằm trong bưu điện.

Here, nằm means to lie / to be situated, so it can sound a little more descriptive:

• The counter is situated inside the post office.

But Quầy ở trong bưu điện is perfectly normal.

In everyday Vietnamese:

• trong by itself means inside / in
• ở trong means be inside / be located inside

So:

• Cái hộp ở trong túi. = The box is in the bag.
• Người ở trong nhà. = The person is inside the house.

Using ở makes the sentence clearly about location. Without ở, the phrase may feel more like a modifier unless the structure makes the meaning obvious.

So for learners, using ở trong is a safe and natural choice when you want to say is in / is inside.