Não quero perder o ônibus amanhã.

In Portuguese, não normally goes directly before the verb it negates.

So:

• Quero = I want
• Não quero = I do not want / I don’t want

This is the standard way to make a sentence negative in Portuguese. Unlike English, you do not need an extra helping verb like do.

So English I don’t want becomes simply não quero.

Portuguese often leaves out the subject pronoun when the verb ending already makes the subject clear.

• quero already means I want
• so eu quero and quero can both mean I want

In this sentence, eu is omitted because it is not necessary.

You could say:

• Eu não quero perder o ônibus amanhã.

But it sounds more natural in many contexts to leave eu out unless you want emphasis or contrast, such as:

• Eu não quero perder o ônibus amanhã, mas ele quer.
  I don’t want to miss the bus tomorrow, but he does.

Quero is the first-person singular present tense form of the verb querer.

• querer = to want
• quero = I want

This is a very common pattern in Portuguese: the verb changes depending on the subject.

For example:

• eu quero = I want
• você quer = you want
• ele/ela quer = he/she wants
• nós queremos = we want

It literally often means to lose, but in this sentence it is being used in the sense of to miss.

So:

• perder o ônibus = to miss the bus

This is very common in Portuguese. The same verb is used in several situations where English might use different verbs:

• perder o ônibus = miss the bus
• perder o trem = miss the train
• perder a chave = lose the key
• perder tempo = waste/lose time

So yes, perder can mean both lose and miss, depending on context.

Portuguese uses definite articles much more often than English does.

So where English says:

• miss the bus

Portuguese says:

• perder o ônibus

The article o means the and is very natural here.

In some situations, Portuguese can omit the article, but with everyday objects like transportation in this kind of sentence, o ônibus is the normal choice.

The accent mark in ônibus shows where the stress falls.

It is pronounced with the stress on the ô syllable:

• Ô-ni-bus

The circumflex accent (ô) also indicates a more closed vowel sound.

This is important because written accents in Portuguese are not optional; they are part of the correct spelling.

Amanhã means tomorrow, and time expressions are often flexible in Portuguese.

All of these can work:

• Não quero perder o ônibus amanhã.
• Amanhã, não quero perder o ônibus.
• Não quero amanhã perder o ônibus. — possible, but less natural in everyday speech

The most natural neutral order here is the one you were given, with amanhã at the end.

Putting amanhã first can give it a little more emphasis:

• Amanhã, não quero perder o ônibus.
  Tomorrow, I don’t want to miss the bus.

Portuguese often uses the present tense to talk about the future when the time is clear from context.

Here:

• quero = present tense
• amanhã = tomorrow

Because amanhã clearly shows future time, Portuguese does not need a special future form here.

This is similar to English sentences like:

• I’m leaving tomorrow
• We travel next week

So Não quero perder o ônibus amanhã is completely natural.

Yes, but it changes the tone.

• Não quero perder o ônibus amanhã = I don’t want to miss the bus tomorrow
• Não vou querer perder o ônibus amanhã literally looks like I am not going to want to miss the bus tomorrow

That second version sounds less direct and usually less natural in this context.

If your goal is simply to say that you do not want to miss the bus tomorrow, não quero perder o ônibus amanhã is the best choice.

Não is pronounced roughly like nowng, but that is only an approximation.

Important points:

• it is one syllable
• the ão sound is nasal
• it does not sound exactly like any single English vowel

Many learners find ão difficult at first because English does not have the same nasal diphthong. You will hear it in many common words:

• não = no / not
• pão = bread
• mão = hand

Listening and repeating native audio helps a lot with this sound.

In real usage, the natural interpretation is I don’t want to miss the bus tomorrow.

Even though perder can mean lose, with ônibus the usual meaning is miss.

If someone somehow literally lost a bus, that would be a very unusual context, so listeners would normally understand perder o ônibus as miss the bus.

Context usually makes the intended meaning obvious.

Yes. In Brazil, ônibus is the standard general word for bus, but you may also hear regional or informal words such as busão.

For example:

• Não quero perder o ônibus amanhã. = neutral/standard
• Não quero perder o busão amanhã. = informal

For learners, ônibus is the safest and most widely accepted choice.

Yes, it is completely natural.

A Brazilian speaker would easily understand it, and it sounds like normal everyday Portuguese.

It is a good example of several common patterns:

• omission of the subject pronoun
• não before the verb
• present tense with future meaning
• perder meaning miss
• use of the definite article before a noun

So this is a very useful model sentence to learn.