Đừng quên đóng cửa sổ trước khi đi làm.

Vietnamese often omits the subject when it is obvious from context.

In Đừng quên đóng cửa sổ trước khi đi làm, the sentence is giving someone a reminder or instruction, so the understood subject is you.

A fuller version could be:

• Bạn đừng quên đóng cửa sổ trước khi đi làm.

But in everyday speech, leaving out bạn is very common if the listener is clear.

Đừng is used for negative commands or warnings, like:

• don’t
• don’t do that
• make sure not to...

So đừng quên means don’t forget.

By contrast, không is the general word for not in statements and questions:

• Tôi không biết. = I don’t know.
• Anh không đi làm hôm nay. = He isn’t going to work today.

So:

• đừng quên = don’t forget
• không quên = not forget / do not forget as a statement, not the usual way to give a command

Yes, đừng quên is a very common expression meaning don’t forget.

Breakdown:

• đừng = don’t
• quên = forget

So the structure is simply:

• đừng + verb

Examples:

• Đừng nói vậy. = Don’t say that.
• Đừng lo. = Don’t worry.
• Đừng quên gọi tôi. = Don’t forget to call me.

So đừng quên đóng cửa sổ literally works like don’t forget close the window, which in natural English becomes don’t forget to close the window.

Vietnamese does not always need a separate word matching English to in verb combinations.

In English, we say:

• forget to close

In Vietnamese, you can often place the second verb directly after the first:

• quên đóng cửa sổ

This is very normal. Vietnamese often links verbs more directly than English does.

Other similar examples:

• Tôi muốn ăn. = I want to eat.
• Anh ấy thích đọc sách. = He likes to read books.
• Đừng quên mang chìa khóa. = Don’t forget to bring the keys.

It is a verb phrase:

• đóng = to close / shut
• cửa sổ = window

So:

• đóng cửa sổ = close the window

The order is:

• verb + object

which is the same basic order as English.

You can use đóng with many things that open and close:

• đóng cửa = close the door
• đóng cửa sổ = close the window
• đóng nắp = close the lid

That is a very common learner question.

Yes, cửa often means door, but it can also refer more generally to an opening, entrance, or framed opening in a wall/building context.

So:

• cửa = door / opening
• cửa sổ = window

You should learn cửa sổ as a full vocabulary item meaning window, not as something you need to translate word-for-word every time.

Similarly:

• cửa ra vào = entrance door
• cửa hàng = shop/store

So cửa appears in many compounds with meanings broader than just door.

trước khi means before in the sense of before doing something.

Breakdown:

• trước = before
• khi = when

Together, trước khi introduces a time clause:

• trước khi đi làm = before going to work / before you go to work

Pattern:

• trước khi + verb phrase

Examples:

• Rửa tay trước khi ăn. = Wash your hands before eating.
• Gọi cho tôi trước khi đến. = Call me before arriving.
• Đừng quên đóng cửa sổ trước khi đi làm. = Don’t forget to close the window before going to work.

Yes, đi làm literally looks like go work, but it naturally means:

• go to work
• go to one’s job
• sometimes more generally be off to work

Breakdown:

• đi = go
• làm = work / do

As a set phrase, đi làm is extremely common.

Examples:

• Tôi đi làm lúc 8 giờ. = I go to work at 8.
• Anh ấy đang đi làm. = He is at work / he has gone to work, depending on context.

So in your sentence, trước khi đi làm is a very natural way to say before going to work.

Yes. Vietnamese pronouns depend a lot on relationship, age, and politeness.

Possible versions:

• Bạn đừng quên đóng cửa sổ trước khi đi làm.
• Anh đừng quên đóng cửa sổ trước khi đi làm.
• Chị đừng quên đóng cửa sổ trước khi đi làm.
• Em đừng quên đóng cửa sổ trước khi đi làm.

These all mean roughly the same thing, but the pronoun changes depending on who you are speaking to.

Leaving the pronoun out makes the sentence more neutral and is common in reminders, notes, or instructions.

It is mostly a reminder or gentle instruction.

Because it uses đừng, it has the grammatical form of a negative command, but đừng quên is often softer than a harsh command. It commonly feels like:

• Don’t forget...
• Make sure you remember to...

Tone and context matter a lot. Said gently, it sounds caring or practical. Said sharply, it can sound more like an order.

You can soften it in several ways.

For example:

• Nhớ đóng cửa sổ trước khi đi làm nhé.
  = Remember to close the window before going to work, okay?

• Đừng quên đóng cửa sổ trước khi đi làm nhé.
  = Don’t forget to close the window before going to work, okay?

• Bạn nhớ đóng cửa sổ trước khi đi làm nhé.
  = Please remember to close the window before going to work.

The particle nhé often makes a sentence sound friendlier and less abrupt.

A rough pronunciation guide is:

• Đừng ≈ dzuhng or yuhng depending on accent
• quên ≈ kwayn
• đóng ≈ dong with a rising tone
• cửa sổ ≈ koo-uh saw
• trước khi ≈ troo-uk kee
• đi làm ≈ dee lahm

A natural rhythm would group it like this:

• Đừng quên | đóng cửa sổ | trước khi đi làm.

If you want the most accurate pronunciation, it is especially important to learn the tones, since tone differences can change the meaning of words.