Learn Hardcore Vietnamese: Ở thành phố, mọi người thường mặc áo sạch nhưng quần lại bẩn. - In the city, people usually wear clean shirts but their pants are dirty.

Ở thành phố ≈ in the city.
Ở is neutral, everyday speech.
Trong thành phố also means in the city, but trong emphasizes inside (more spatial, like “inside the city limits”).
Tại thành phố can also mean at / in the city, but tại is more formal or written (e.g. news, official language), and less common in casual speech.

In spoken, natural Vietnamese, Ở thành phố is the most typical choice here.

Why is Ở thành phố put at the beginning of the sentence with a comma?

Vietnamese often puts information about time or place at the beginning of the sentence as a topic:

Ở thành phố, mọi người thường mặc áo sạch nhưng quần lại bẩn.
→ In the city, people usually wear clean shirts but their pants are dirty.

This structure is very common:

Hôm qua, tôi đi chợ. = Yesterday, I went to the market.
Ở nhà, anh ấy rất lười. = At home, he is very lazy.

The comma reflects a slight pause after the topic. You could also say:

Mọi người ở thành phố thường mặc áo sạch nhưng quần lại bẩn.

That’s also correct and natural; the meaning is the same, just a slightly different emphasis.

What exactly does mọi người mean? Is it “everyone” or “people”?

Literally, mọi người = every person(s). In practice it usually corresponds to:

people (general)
everyone / everybody

In this sentence:

mọi người thường mặc áo sạch ≈ people usually wear clean shirts
(or everyone usually wears clean shirts)

It refers to people in general, not specific individuals. It’s a very common phrase in Vietnamese.

What does thường mean and where does it go in the sentence?

thường means usually / often. It is an adverb of frequency and typically appears before the main verb:

mọi người thường mặc áo sạch
→ people usually wear clean shirts

Other examples:

Tôi thường ăn sáng lúc 7 giờ. = I usually eat breakfast at 7.
Cô ấy thường đi bộ đến trường. = She often walks to school.

You rarely move thường after the verb; mặc thường áo sạch is incorrect. The natural position is:

subject + thường + verb (+ object)

Why does the sentence say mặc áo and quần separately? Why not just mặc quần áo for “wear clothes”?

Vietnamese uses áo and quần in a specific way:

áo = upper-body clothing (shirt, blouse, jacket, etc.)
quần = pants/trousers/shorts (lower-body clothing)
quần áo = clothes (in general), literally “pants and shirts”

In this sentence:

mặc áo sạch = wear a clean shirt / upper-body garment
quần lại bẩn = (their) pants, however, are dirty

So the sentence contrasts áo vs quần, upper vs lower clothing:

people usually wear clean shirts but their pants are dirty.

If you said:

mọi người thường mặc quần áo sạch
→ people usually wear clean clothes (no contrast between top and bottom)

you would lose the specific contrast that makes the sentence humorous/striking.

Why is there no word for “their” before áo and quần?

Vietnamese often omits possessive pronouns when it is obvious from context whose thing is being talked about.

mọi người thường mặc áo sạch
Literally: people usually wear clean shirts
Understood: people usually wear their shirts clean

It would sound redundant or unnatural to say mặc áo của họ (“wear shirts of them”) here.

Similarly:

Tôi đau đầu. = My head hurts.
Cô ấy rửa tay. = She washes her hands.

No explicit my / her / their, but it is understood.

Why don’t we see a verb like “to be” before sạch and bẩn? In English we say “are clean / are dirty”.

In Vietnamese, adjectives often function like stative verbs and do not need a separate “to be” verb in simple descriptions.

áo sạch = (the) shirt is clean
quần bẩn = (the) pants are dirty

So:

mọi người thường mặc áo sạch
literally: people usually wear shirt clean
meaning: people usually wear clean shirts
quần lại bẩn
literally: pants again dirty
meaning: but the pants are dirty

You only add là (a kind of “to be”) mainly before nouns, not before adjectives in basic descriptions:

Cô ấy là giáo viên. = She is a teacher.
Cô ấy đẹp. (Not là đẹp) = She is beautiful.

What is the role of nhưng and lại together? Could we just say nhưng quần bẩn?

Yes, you could say:

… mặc áo sạch nhưng quần bẩn.

That is grammatically correct and means:

… wear clean shirts but the pants are dirty.

However, lại adds a nuance of contrast / unexpectedness, roughly:

nhưng quần lại bẩn ≈ but (on the other hand) the pants are dirty
or but the pants, however, are dirty

lại here emphasizes that the second part is surprisingly different from the first.

Other examples of lại in this contrastive sense:

Trời đang nắng, lại mưa rồi. = It was sunny, but now it’s raining (contrary shift).
Anh ấy giàu, em lại nghèo. = He is rich, but I am poor.

So nhưng … lại … is a very natural pattern to highlight a stronger contrast.

Why is there no verb before quần lại bẩn? Shouldn’t it say quần (thì) lại bẩn or something?

The second clause is a bit shortened by ellipsis, which is very common in Vietnamese when the meaning is clear from context.

Fuller versions could be:

… mọi người thường mặc áo sạch nhưng quần (thì) lại bẩn.
… nhưng quần (của họ) lại bẩn.

Omitting thì or của họ is natural because:

The subject quần is clear.
The contrast with the previous clause is obvious.

Vietnamese often drops unnecessary words to keep sentences short and fluent.

How do we know this sentence is talking about a habitual action (usually / often), not the past or future?

There is no tense inflection in Vietnamese verbs, so time and aspect are indicated by adverbs and context.

Here:

thường = usually / often → indicates habitual action.
No time marker like hôm qua (yesterday) or mai (tomorrow), so we read it as a general statement.

If you wanted to be explicit about time, you could say:

Trước đây ở thành phố, mọi người thường mặc áo sạch nhưng quần lại bẩn.
→ In the past, in the city, people usually wore clean shirts but their pants were dirty.
Sau này ở thành phố, mọi người sẽ thường mặc áo sạch nhưng quần lại bẩn.
→ In the future, in the city, people will usually wear clean shirts but their pants will be dirty.

But without such markers, with thường, we naturally interpret it as a present/general habit.

Is Ở thành phố, mọi người thường mặc áo sạch nhưng quần lại bẩn natural Vietnamese? Are there alternative natural ways to say the same idea?

Yes, the original sentence is natural and clear, especially in spoken or informal written Vietnamese. Some natural variations include:

Mọi người ở thành phố thường mặc áo sạch nhưng quần lại bẩn.
Ở thành phố, người ta thường mặc áo sạch nhưng quần lại bẩn.
- người ta ≈ “people / they (in general)”

If you want more explicit contrast, you could slightly emphasize:

Ở thành phố, áo thì thường sạch nhưng quần lại bẩn.
→ In the city, shirts are usually clean, but pants, however, are dirty.

All of these are idiomatic; the differences are in nuance and emphasis, not in basic grammar.