Eu não quero comprar nada hoje.

Yes, you can often leave it out.

Portuguese is a pro-drop language, which means subject pronouns are often omitted when the verb already makes the subject clear.

• Eu não quero comprar nada hoje. = I don’t want to buy anything today.
• Não quero comprar nada hoje. = same meaning

Because quero clearly means I want, eu is not required.
Including eu can add:

• emphasis
• contrast
• a slightly more explicit tone

For example:

• Eu não quero comprar nada hoje, mas ele quer.
  = I don’t want to buy anything today, but he does.

In Portuguese, the normal negative word não goes before the conjugated verb.

So:

• quero = I want
• não quero = I do not want

This is just the standard placement in Portuguese.
English uses do not plus the main verb, but Portuguese usually just puts não before the verb:

• Eu quero = I want
• Eu não quero = I don’t want

You do not need a separate word like English do here.

Yes, it is a kind of double negative by English logic, but in Portuguese this is normal and correct.

Portuguese commonly uses negative concord, which means multiple negative words can appear in the same sentence to express just one negative idea.

So:

• Eu não quero comprar nada hoje.

literally looks like:

• I not want buy nothing today

But the real meaning is:

• I don’t want to buy anything today

This is standard Portuguese, not a mistake.

More examples:

• Não vi ninguém. = I didn’t see anyone.
• Nunca faço isso. = I never do that.
• Não tenho nenhum dinheiro. = I don’t have any money.

Because in negative sentences, Portuguese often uses nada where English uses anything.

So in:

• Eu não quero comprar nada hoje

nada is literally nothing, but in natural English translation it becomes anything because that sounds normal after a negative verb.

Compare:

• Quero comprar alguma coisa. = I want to buy something.
• Não quero comprar nada. = I don’t want to buy anything.

So the important idea is:

• after a negative, Portuguese often keeps a negative word
• English often switches to anything / anyone / ever

Because after querer (to want), Portuguese usually uses another verb in the infinitive.

Structure:

• querer + infinitive

So:

• quero comprar = I want to buy
• quero comer = I want to eat
• quero sair = I want to leave/go out

This works very much like English want to + verb, except Portuguese does not use a separate word equivalent to to in this structure.

So:

• quero comprar not
• quero a comprar not
• quero de comprar

Yes. Querer is an irregular verb.

Its infinitive is:

• querer = to want

But the eu form is:

• eu quero = I want

Some present-tense forms are:

• eu quero
• você quer
• ele/ela quer
• nós queremos
• vocês querem
• eles/elas querem

A learner might expect something more regular, but quero is the correct first-person singular form.

Usually, no. The natural standard order is:

• Eu não quero comprar nada hoje.

The negation não normally goes before the conjugated verb, which here is quero.

So:

• não quero = I don’t want

Putting não later can change the structure or sound unnatural in this sentence.

Yes, hoje can move around, but the version with hoje at the end is very natural.

Common options:

• Eu não quero comprar nada hoje.
• Hoje eu não quero comprar nada.
• Eu hoje não quero comprar nada. (possible, but often more marked)

The end position is very common because it feels neutral and natural.

Putting hoje first can add slight emphasis to today:

• Hoje eu não quero comprar nada.
  = Today, I don’t want to buy anything.

They are related, but they are used differently.

• nada = nothing / anything
• nenhum / nenhuma = no / not any

Examples:

• Não quero comprar nada hoje.
  = I don’t want to buy anything today.

• Não quero comprar nenhum livro hoje.
  = I don’t want to buy any book today.

Use nada when you mean nothing / anything in a general sense.
Use nenhum / nenhuma before a noun:

• nenhum livro
• nenhuma roupa
• nenhum carro

It is neutral and completely normal in both speech and writing.

Nothing in the sentence is especially formal or especially casual. It works in everyday Brazilian Portuguese.

You could hear or say it in many situations:

• talking to a friend
• answering a store clerk
• talking to family
• making a general statement

If you wanted to sound a bit softer, you might say:

• Hoje eu não estou a fim de comprar nada.
  = I’m not in the mood to buy anything today.

But Eu não quero comprar nada hoje is perfectly standard.

The tilde ~ shows nasalization.

So não is pronounced with a nasal sound, roughly like nowng said through the nose, though there is no exact English equivalent.

Important points:

• não is one syllable
• the vowel is nasal
• the final o is not pronounced like a strong English oh

The tilde in ã is not just decoration; it changes the sound.

In Brazilian Portuguese, learners often need practice making the vowel nasal instead of saying a plain nao.

A rough pronunciation guide:

• quero ≈ KEH-roo

  • the que here sounds like keh
  • the final o in Brazilian Portuguese is often closer to oo

• comprar ≈ kom-PRAHR

  • stress on the last syllable
  • the r at the end varies by region, often sounding like a soft h in many Brazilian accents

• hoje ≈ OH-zhee or OH-jee, depending on accent

  • the j in Portuguese sounds like the s in measure or the zh sound

This is only approximate, but it helps as a starting point.

Not in correct English translation.

Even though Portuguese uses não ... nada, the correct meaning in English is:

• I don’t want to buy anything today

In Portuguese, não ... nada is normal grammar.
In standard English, I don’t want to buy nothing is usually considered nonstandard or dialectal.

So when translating, think:

• Portuguese negative + negative word
• English usually negative + any-word

Not directly in this sentence.

• alguma coisa = something
• nada = nothing / anything in negative contexts

So:

• Eu quero comprar alguma coisa hoje.
  = I want to buy something today.

But if the sentence is negative, nada is the natural choice:

• Eu não quero comprar nada hoje.

You could also hear:

• Eu não quero comprar coisa nenhuma hoje.

This also means:

• I don’t want to buy anything today

It is emphatic and very common in spoken Brazilian Portuguese.

Usually it means a current desire or intention, but context matters.

• Eu não quero comprar nada hoje most naturally means
  I don’t want to buy anything today / I’m not planning to buy anything today

Because of hoje, it clearly refers to today, so it sounds like a present decision or feeling.

Portuguese present tense often covers meanings that English may express with either:

• I don’t want
• I’m not wanting (which English usually does not say)
• I’m not looking to buy anything today
• I don’t feel like buying anything today

So the Portuguese present tense is simple, but the exact English wording depends on context.