Tối nay, tôi không muốn ra khỏi nhà vì trời rất lạnh.

Tối nay means tonight / this evening. In Vietnamese, time expressions very often come at the beginning of the sentence to set the time frame first.

So:

• Tối nay, tôi không muốn ra khỏi nhà vì trời rất lạnh. = Tonight, I don't want to leave the house because it's very cold.

You could also place the time later in some contexts, but putting it first is extremely natural.

The comma separates the time expression from the main statement. It works a lot like English when we say:

• Tonight, I don't want to go out...

In Vietnamese, punctuation is somewhat flexible in casual writing, so you may see:

• Tối nay tôi không muốn ra khỏi nhà vì trời rất lạnh.

with no comma. Both are fine.

You do not always have to include tôi if the subject is already clear from context. Vietnamese often drops subjects when they are understood.

So all of these can work depending on context:

• Tối nay, tôi không muốn ra khỏi nhà vì trời rất lạnh.
• Tối nay, không muốn ra khỏi nhà vì trời rất lạnh.

The version with tôi is clearer and is especially helpful for learners.

Also, tôi is a neutral word for I. In real conversation, Vietnamese often uses kinship-style pronouns instead, depending on who is speaking to whom.

In Vietnamese, không usually goes before the verb to negate it.

Here:

• muốn = to want
• không muốn = do not want

So:

• tôi không muốn = I do not want

This is a very common pattern:

• tôi không biết = I don't know
• anh ấy không ăn = he doesn't eat
• chúng tôi không đi = we aren't going

Muốn means to want. It is followed directly by another verb or verb phrase.

Pattern:

• muốn + verb

Examples:

• muốn đi = want to go
• muốn ăn = want to eat
• muốn ngủ = want to sleep

In your sentence:

• không muốn ra khỏi nhà = don't want to go out / leave the house

Vietnamese does not need a word like English to in want to go.

This part is built from smaller pieces:

• ra = go out / move outward
• khỏi = out of / away from
• nhà = house / home

So ra khỏi nhà literally suggests go out from the house or leave the house.

A learner may notice that ra and khỏi both seem to express outward movement. That is normal in Vietnamese. Verbs of motion often combine with direction words to give a more precise sense of movement.

So this phrase is very natural.

Usually, ra khỏi nhà is the natural full expression for go out of the house / leave home.

• ra nhà is generally not correct for this meaning.
• khỏi nhà by itself is less complete in this structure.

You may also hear:

• đi ra ngoài = go outside
• rời khỏi nhà = leave the house/home
• ra ngoài = go out/outside

But for this sentence, ra khỏi nhà is perfectly natural.

Vì means because. It introduces the reason.

Structure:

• main statement + vì + reason

So:

• tôi không muốn ra khỏi nhà vì trời rất lạnh = I don't want to leave the house because it's very cold

A very close alternative is bởi vì, which also means because, but vì is shorter and very common.

Trời literally means sky, but in many everyday expressions it functions like the weather / it in English.

So:

• trời lạnh = it is cold / the weather is cold
• trời nóng = it is hot
• trời mưa = it is raining

English uses a dummy subject in weather expressions, like it is cold. Vietnamese often uses trời instead.

You can sometimes omit it in casual speech if the context is obvious, but trời rất lạnh is the standard, clear phrasing.

Rất means very. It comes before adjectives.

So:

• lạnh = cold
• rất lạnh = very cold

This is the normal order:

• rất đẹp = very beautiful
• rất khó = very difficult
• rất vui = very happy

So trời rất lạnh literally follows the pattern:

• weather + very + cold

In some ways, yes, but there are important differences.

The sentence structure is roughly:

• Time + subject + negation + want + motion phrase + because + weather phrase

More literally:

• Tonight, I not want go out of house because weather very cold.

Key differences from English:

• No do-support: Vietnamese says không muốn, not something like do not want
• No article before nhà: Vietnamese usually does not use the/a in the same way English does
• No linking verb is in trời rất lạnh: Vietnamese often does not need a word equivalent to is

Vietnamese often omits the equivalent of to be when describing qualities.

So:

• trời rất lạnh literally looks like weather very cold
• natural English translation: it is very cold

This is extremely common in Vietnamese:

• Cô ấy đẹp. = She is beautiful.
• Anh ấy mệt. = He is tired.
• Hôm nay nóng. = Today is hot.

So the absence of is is normal.

Yes. Nhà can mean both house and home, depending on context.

In this sentence, English might translate it as either:

• leave the house
• leave home
• go out

All are reasonable depending on the intended tone.

Vietnamese nhà is broader than English house in many cases and often refers naturally to one’s home.

Yes. That is also natural.

Compare:

• ra khỏi nhà = leave the house / go out of the house
• đi ra ngoài = go outside / go out

Your alternative:

• Tối nay tôi không muốn đi ra ngoài vì trời rất lạnh.

means nearly the same thing. It may feel a little more like go outside or go out, while ra khỏi nhà highlights leaving the home itself.

Both are good Vietnamese.

It is mostly neutral and works in both spoken and written Vietnamese.

Why it feels neutral:

• tôi is a neutral pronoun
• the grammar is straightforward
• the vocabulary is common and standard

In more casual speech, a person might change the pronoun or shorten parts depending on the relationship and context. But as a model sentence for learning, this one is very natural and standard.

A good way to learn it is in chunks rather than word-by-word.

Useful chunks:

• Tối nay = tonight
• tôi không muốn... = I don't want to...
• ra khỏi nhà = leave the house / go out
• vì trời rất lạnh = because it's very cold

This helps you build similar sentences:

• Tối nay, tôi không muốn đi làm vì tôi rất mệt.
• Hôm nay, tôi không muốn ra ngoài vì trời mưa.
• Ngày mai, tôi muốn ở nhà vì cần nghỉ ngơi.

Learning chunks makes Vietnamese sentence patterns much easier to reuse.