Cậu nằm ở đây nhé.

Here, cậu is a pronoun meaning you.

It is commonly used for:

• a friend
• someone around the same age
• someone younger in a familiar, casual relationship

It is not the most neutral or universal way to say you in Vietnamese. Vietnamese pronouns depend a lot on relationship, age, and social context.

Also, cậu can mean other things in different contexts, such as maternal uncle, but in this sentence it clearly means you.

No. Vietnamese does not have just one all-purpose word for you.

Whether cậu sounds right depends on who you are talking to. For example:

• with a close friend: cậu may be natural
• with an older person: usually not appropriate
• with a stranger: often not the best choice
• in polite situations: other pronouns are preferred

Depending on the situation, Vietnamese might use:

• bạn
• anh
• chị
• em
• con
• cháu

So the sentence pattern stays the same, but the pronoun may change:

• Anh nằm ở đây nhé.
• Chị nằm ở đây nhé.

Nằm means to lie down, to be lying, or to recline.

In this sentence, it most naturally means:

• lie here
• lie down here

It does not automatically mean sleep. If you want to say sleep, the usual verb is ngủ.

So:

• nằm = lie down / be lying
• ngủ = sleep

Because the sentence is about body position, not necessarily about sleeping.

If someone says Cậu nằm ở đây nhé, they are telling the person to move into a lying position in that place.

That could happen:

• at home
• in a hospital or clinic
• during a massage
• when someone is tired or injured

If the speaker wanted to tell someone to sleep here, they would more likely use ngủ:

• Cậu ngủ ở đây nhé.

Ở is related to location. In ở đây, it helps express here as a place.

So:

• đây = this place / here
• ở đây = at here / here

In natural English we just say here, but Vietnamese often uses ở when giving a location after a verb:

• ngồi ở đây = sit here
• đợi ở đây = wait here
• nằm ở đây = lie here

The normal Vietnamese order is:

verb + location

So:

• nằm ở đây = lie here
• ngồi ở đây = sit here
• đứng ở đây = stand here

Putting ở đây first is possible in some contexts for emphasis, but it is not the neutral basic order.

So Cậu nằm ở đây nhé follows the standard, natural pattern.

Nhé is a sentence-final particle that softens the sentence.

It can add a feeling like:

• okay?
• all right?
• please, okay
• just do that for me, okay?

It makes the sentence sound:

• gentler
• friendlier
• less blunt
• more cooperative

So without nhé, Cậu nằm ở đây can sound more direct.
With nhé, it sounds softer and more caring.

It can be any of those depending on context, but most often it feels like a gentle instruction or soft request.

Because of nhé, it usually does not sound harsh. It often feels like:

• a friendly instruction
• a caring request
• a suggestion the speaker expects the listener to follow

For example, it could be something a doctor, parent, friend, or caregiver says.

Yes. That is very natural.

Vietnamese often omits the subject when it is already clear from context. So if you are directly talking to someone, you can simply say:

Nằm ở đây nhé.

That may sound more natural than repeating the pronoun every time.

Including cậu can:

• make it clearer who you are addressing
• add a slightly more personal tone
• create contrast, as in speaking to one person rather than another

Yes, usually.

Đây refers to something close to the speaker, so ở đây means here.

Compare:

• đây = here, near me
• đó = there, often nearer you or already identified
• kia = over there, farther away

So:

• nằm ở đây nhé = lie here
• nằm ở đó nhé = lie there
• nằm ở kia nhé = lie over there

It is casual and friendly, not highly formal.

The formality comes mainly from:

• the pronoun cậu
• the softening particle nhé

This sounds suitable in informal or familiar situations. In a more polite or service-oriented context, Vietnamese often changes the pronoun and may add something like ạ or mời.

For example:

• Mời anh nằm ở đây ạ.
• Chị nằm ở đây nhé.

So the structure is fine, but the level of politeness depends heavily on the pronouns and particles chosen.