Đừng lừa bạn.

Đừng is the usual word for a negative command in Vietnamese. It works like English don’t.

So the pattern is:

• đừng + verb

Examples:

• Đừng nói. = Don’t speak.
• Đừng đi. = Don’t go.
• Đừng lừa... = Don’t deceive / don’t trick...

So in Đừng lừa bạn, đừng is what turns the sentence into a prohibition.

In Vietnamese, the subject is often left out when it is obvious, especially in commands.

In English, we usually understand an invisible you in commands:

• Don’t run.
• Don’t lie.

Vietnamese does the same thing:

• Đừng chạy.
• Đừng lừa bạn.

The understood subject is you, but it does not need to be said.

If a speaker wants to include the subject for emphasis or politeness, they can, but it depends on the relationship between speakers.

Lừa means to trick, cheat, or deceive someone.

It is a very common everyday verb. It usually takes a direct object:

• lừa người khác = deceive other people
• lừa bạn = deceive a friend

Related forms:

• lừa dối = deceive, betray trust; often a bit fuller or more formal
• đánh lừa = fool, mislead, trick

So lừa by itself is completely normal here.

Because Vietnamese normally uses verb + object word order, just like English.

Structure here:

• đừng = don’t
• lừa = deceive
• bạn = friend

So the sentence is built like:

• Don’t + deceive + friend

That is normal Vietnamese word order.

In Vietnamese, bạn can mean either:

• friend
• you (in a neutral, informal-to-polite way)

That is something learners often notice quickly.

In this sentence, though, bạn is most naturally understood as friend, because it comes after lừa as the object of the verb.

Still, taken by itself, the sentence is a little context-dependent, because bạn is such a flexible word in Vietnamese.

Vietnamese does not use articles the way English does, so there is no direct equivalent of a or the in most cases.

Also, possession is often left unstated if the context already makes it clear.

So a bare noun like bạn can appear naturally without extra words.

If a speaker wants to be more specific, they might say something like:

• bạn ấy = that friend
• người bạn đó = that friend
• bạn của anh ấy = his friend

So bạn by itself is not strange from a grammar point of view.

It is grammatically fine, but by itself it can feel a little bare or under-specified.

In real conversation, Vietnamese often adds more context, for example:

• Đừng lừa bạn ấy. = Don’t deceive that friend.
• Đừng lừa bạn bè. = Don’t deceive your friends / friends.
• Đừng lừa người ta. = Don’t deceive people / that person.

So the sentence is good for learning the structure đừng + verb + object, but in real life a speaker might often make the object more specific.

No. Bạn by itself already means friend, so Đừng lừa bạn is structurally possible.

However, người bạn is also a valid phrase meaning friend, and it can sound a bit more explicitly noun-like in some contexts.

Compare:

• bạn = friend
• người bạn = a friend / friend

Both are correct, but bạn alone is very common.

A rough guide:

• Đừng: the đ is like English d, not English z or y
• lừa: starts with a clear l
• bạn: ends with n, and has the heavy nặng tone

The tricky parts for English speakers are usually:

• ư, which has no exact English equivalent
• the tones

Tone-wise:

• đừng has a falling tone
• lừa also has a falling tone
• bạn has the nặng tone, which is low and short

So the tones are an important part of saying the sentence correctly.

Yes. Đừng có is possible and adds a more emphatic or sometimes more colloquial feeling.

Compare:

• Đừng lừa bạn. = Don’t deceive your friend.
• Đừng có lừa bạn. = Don’t you go deceiving your friend.

So đừng có often sounds stronger, more emotional, or more conversational.