Learn Hardcore Vietnamese: Đừng mặc áo bẩn hay quần bẩn nếu bạn muốn ở khách sạn sạch. - Don't wear dirty shirts or dirty pants if you want to stay at a clean hotel.

Đừng + verb = Don’t + verb
- Đừng mặc áo bẩn… = Don’t wear dirty clothes…
Không + verb = do not / don’t in a statement, not a command
- Tôi không mặc áo bẩn. = I don’t wear dirty clothes.

So:

Đừng mặc áo bẩn… = Don’t wear dirty clothes…
Không mặc áo bẩn… on its own sounds incomplete, like a fragment of a rule, not a direct instruction.

You can also hear đừng có mặc…, which is a bit more emphatic or colloquial: Don’t you go wearing…

Why is bẩn repeated in áo bẩn hay quần bẩn? Could we just say it once?

Repeating bẩn makes it very clear that both items are potentially dirty:

áo bẩn hay quần bẩn = dirty shirt or dirty pants

If you say:

áo hay quần bẩn

it can be understood as:

“shirt or dirty pants” (only quần is clearly modified by bẩn), or
“shirt or pants that are dirty” (guessed from context)

Native speakers often still understand it, but áo bẩn hay quần bẩn is clearer and more balanced.

You can also say:

áo quần bẩn = dirty clothes (treating áo quần together as “clothes”)

What does hay mean here, and how is it different from hoặc?

Both hay and hoặc can mean or, but their usage is a bit different.

hay
- Very common in questions offering a choice:
  - Bạn muốn trà hay cà phê? = Do you want tea or coffee?
- Also used in imperatives and negatives like this sentence:
  - Đừng hút thuốc hay uống rượu. = Don’t smoke or drink alcohol.
- Sounds more natural here: Đừng mặc áo bẩn hay quần bẩn…
hoặc
- More neutral, often used in plain statements:
  - Bạn có thể uống trà hoặc cà phê. = You can drink tea or coffee.
- In a prohibition like this, hay is generally better than hoặc.

You could say Đừng mặc áo bẩn hoặc quần bẩn, but hay is the more idiomatic choice in an instruction like this.

Why is the word order áo bẩn and khách sạn sạch, not bẩn áo or sạch khách sạn?

In Vietnamese, adjectives normally come after the noun they describe:

áo bẩn = dirty shirt (literally: shirt dirty)
quần bẩn = dirty pants
khách sạn sạch = clean hotel

This applies generally:

người tốt = good person
nhà mới = new house
thức ăn ngon = tasty food

Putting the adjective before the noun (like bẩn áo, sạch khách sạn) is not standard grammar and sounds wrong in modern Vietnamese, except in certain fixed expressions or poetic/literary styles, which don’t apply here.

Where is the verb to be in áo bẩn or khách sạn sạch? Why is there no word like is/are?

Vietnamese usually doesn’t use an explicit “to be” (like is/are) before adjectives.

áo bẩn can mean:
- as a noun phrase: a dirty shirt
- as a clause (with context): the shirt is dirty
khách sạn sạch can mean:
- a clean hotel
- (in some contexts) the hotel is clean

If you really want to emphasize the idea “X is Y”, you can sometimes use là, but not before adjectives in the simple way English does. You might say:

Cái áo này bẩn. = This shirt is dirty.
Khách sạn này rất sạch. = This hotel is very clean.

So in Đừng mặc áo bẩn…, bẩn is just an adjective modifying áo; no extra “is” is needed.

What exactly do áo and quần mean? Are they specific kinds of clothes?

Yes, they are quite general clothing words:

áo = any upper‑body garment (shirt, blouse, T‑shirt, jacket, coat, etc.), depending on context
quần = any type of pants/trousers (jeans, slacks, shorts are often quần short, etc.)

If you need to be specific, you usually add another word:

áo sơ mi = dress shirt
áo thun = T‑shirt
áo khoác = jacket
quần jean = jeans
quần tây = dress pants

In this sentence, áo bẩn hay quần bẩn is just dirty tops or dirty bottoms—basically, dirty clothes on your upper or lower body.

Why is there no word showing plural, like dirty shirts or dirty pants?

Vietnamese usually does not mark plural on nouns unless it’s important to emphasize “more than one”.

áo bẩn can mean:
- a dirty shirt
- dirty shirts
quần bẩn can mean:
- dirty pants (one pair)
- dirty pants (several pairs)
khách sạn sạch can mean:
- a clean hotel
- clean hotels (in general)

If you want to emphasize plurality, you can add:

những or các:
- những cái áo bẩn = the dirty shirts / some dirty shirts
- các khách sạn sạch = the clean hotels

But in general advice like this, Vietnamese is happy with the bare noun. Context tells you that it applies to any such clothes, singular or plural.

Why is there no classifier like cái, chiếc, or cái áo in this sentence?

Classifiers (like cái, chiếc, con, tấm, etc.) are often used when you:

count things: một cái áo, hai chiếc quần
point at or specify things: cái áo này, chiếc quần kia

But when you’re talking in general, especially in rules or advice, it’s common to omit classifiers:

Đừng mặc áo bẩn. = Don’t wear dirty shirts (in general).
Không ăn thịt sống. = Don’t eat raw meat.

You could say:

Đừng mặc cái áo bẩn hay cái quần bẩn.

That sounds like you’re referring to particular specific items you both know about. The version without classifiers is more general and fits a rule or guideline.

What does ở mean here in muốn ở khách sạn sạch? Is it “stay at” or “be at”?

The verb ở is quite flexible. It covers several English meanings:

to be in/at (location)
to stay (at) somewhere (for a while)
to live somewhere (long term), often with sống: ở / sống ở Hà Nội

In this sentence:

muốn ở khách sạn sạch = want to stay in/at a clean hotel

So ở khách sạn naturally means stay at a hotel in this context. You could also say:

muốn ở lại khách sạn sạch – adding lại can emphasize “remain/stay there”, but it’s not needed here.

Why is there no word for a in khách sạn sạch (a clean hotel)? How do I say a in Vietnamese?

Vietnamese has no direct equivalent of the English article a/an. An unmarked noun can be:

general (hotels in general)
singular (a hotel)
plural (hotels)

In this sentence:

ở khách sạn sạch = stay in a clean hotel / stay at clean hotels (depending on context)

You can add một (one) when you really want to stress one individual hotel:

ở một khách sạn sạch = stay in a/one clean hotel

But in many contexts, especially with muốn ở khách sạn sạch as a general condition, native speakers prefer to omit một unless the “one” is important.

Can I say áo quần bẩn or áo hay quần bẩn instead of áo bẩn hay quần bẩn?

Yes, but the nuance is slightly different:

Đừng mặc áo quần bẩn nếu…
- áo quần together commonly means clothes.
- This sounds like: Don’t wear dirty clothes if…
- It’s natural and common.
Đừng mặc áo hay quần bẩn nếu…
- Grammatically possible.
- As mentioned earlier, it can be slightly less clear that bẩn applies to both áo and quần, but context usually fixes that.
- Sounds a bit less nicely balanced than áo bẩn hay quần bẩn, which puts bẩn directly after each noun.

So:

For “dirty clothes” in general: áo quần bẩn is good.
For explicit “dirty shirts or dirty pants”: áo bẩn hay quần bẩn is clearest.

Does this sentence sound rude? How could I make it softer or more polite?

Đừng + verb is a direct prohibition. With bạn as the pronoun, it’s fairly neutral and direct, like telling a peer or customer in plain language:

Đừng mặc áo bẩn hay quần bẩn nếu bạn muốn ở khách sạn sạch.

Ways to soften it:

Use a more advisory form:
- Bạn không nên mặc áo bẩn hay quần bẩn nếu muốn ở khách sạn sạch.
  = You shouldn’t wear dirty clothes if you want to stay at a clean hotel.
Add a softening particle:
- Đừng mặc áo bẩn hay quần bẩn nhé, nếu bạn muốn ở khách sạn sạch.
  nhé makes it sound more friendly / less harsh.
Remove bạn if it’s clearly a general rule (like on a sign), making it more impersonal:
- Đừng mặc áo bẩn hay quần bẩn nếu muốn ở khách sạn sạch.

So the original is not extremely rude, but it is quite direct; the versions above are more polite or advisory.