O arquivo já está no computador, mas o teclado e o mouse estão ao lado da impressora.

Portuguese uses definite articles much more often than English.

In this sentence, the speaker is referring to specific, identifiable things:

• o arquivo = the file
• o computador = the computer
• o teclado = the keyboard
• o mouse = the mouse
• a impressora = the printer

In English, you might sometimes drop articles in certain contexts, but in Portuguese they are very common with everyday nouns.

Also note the genders:

• o arquivo — masculine
• o computador — masculine
• o teclado — masculine
• o mouse — usually treated as masculine in Brazilian Portuguese
• a impressora — feminine

Já usually means already.

So:

• O arquivo está no computador = The file is on the computer.
• O arquivo já está no computador = The file is already on the computer.

It adds the idea that this condition is already true now, often implying:

• it has been done
• it is no longer pending
• this part is settled

Very common in Brazilian Portuguese:

• Já chegou? = Has it already arrived?
• Já fiz isso. = I already did that.

Portuguese has two main verbs meaning to be: ser and estar.

Here, estar is used because the sentence talks about location:

• O arquivo já está no computador.
• O teclado e o mouse estão ao lado da impressora.

A very useful rule:

• ser = identity, classification, essential characteristics
• estar = location, condition, temporary state

So for location, you normally use estar:

• O livro está na mesa. = The book is on the table.
• Ela está em casa. = She is at home.

Because the subject changes.

• O arquivo já está no computador

  • subject = o arquivo = singular
  • so the verb is singular: está

• o teclado e o mouse estão ao lado da impressora

  • subject = o teclado e o mouse = two things
  • so the verb is plural: estão

This is normal subject-verb agreement.

A quick pattern:

• ele está = he/it is
• eles estão = they are

Because Portuguese often contracts em + o/a/os/as.

Here:

• em + o = no
• so no computador = in/on the computer

Other common contractions:

• em + a = na
• em + os = nos
• em + as = nas

Examples:

• na mesa = on the table
• nos livros = in the books
• nas caixas = in the boxes

So em o computador is not the normal form; no computador is.

Ao lado de means next to / beside / at the side of.

So:

• ao lado da impressora = next to the printer / beside the printer

The form da is a contraction:

• de + a = da

And ao is also a contraction:

• a + o = ao

So literally, the structure is:

• ao lado de a impressora which becomes
• ao lado da impressora

You will see this kind of contraction all the time in Portuguese.

Related forms:

• ao lado do computador = next to the computer
• ao lado dos livros = next to the books
• ao lado das caixas = next to the boxes

Yes. In Brazilian Portuguese, ao lado de and do lado de are both very common and usually mean the same thing: beside / next to.

So these are both natural:

• estão ao lado da impressora
• estão do lado da impressora

Ao lado de can sound a little more standard or neutral in some contexts, but both are perfectly normal in everyday speech.

Because in Portuguese, when two nouns are joined by e (and), they usually form a plural subject.

So:

• o teclado e o mouse = the keyboard and the mouse
• together they are they
• therefore: estão

This works the same way with other nouns:

• O livro e a caneta estão na mochila.
• A mesa e a cadeira estão na sala.

The verb agrees with the whole subject, not just the nearest noun.

Yes. In Brazilian Portuguese, mouse is very commonly used as a borrowed word from English.

It is normally treated as masculine:

• o mouse

So you will hear:

• o mouse
• um mouse novo
• meu mouse

In everyday Brazilian Portuguese, this is completely normal. Some people may also use less common alternatives in special contexts, but mouse is the standard everyday word.

Most Brazilians pronounce mouse approximately like the English word mouse, but adapted to Portuguese pronunciation.

A rough guide:

• mouse → sounds close to mau-se

The exact pronunciation can vary a bit by region and speaker, but if you say something close to the English word, you will generally be understood.

Great question. Portuguese often uses em for locations where English might use in or on, depending on context.

So:

• no computador literally looks like in the computer
• but in real usage it often corresponds to English on the computer

For digital content, Portuguese commonly says:

• O arquivo está no computador. Even though English prefers:
• The file is on the computer.

This is a translation difference, not a grammar mistake.

Mas means but.

It connects two ideas with a contrast:

• The file is already on the computer
• but the keyboard and the mouse are beside the printer

The contrast is mild: one thing is in its expected place, while the other items are somewhere else.

Important: mas is the conjunction but. Do not confuse it with mais, which means more.

Examples:

• Quero ir, mas estou cansado. = I want to go, but I’m tired.
• Quero mais café. = I want more coffee.

Normally, no—not in a standard full sentence like this.

These sound natural:

• O arquivo já está no computador.
• O teclado e o mouse estão ao lado da impressora.

If you remove the articles, the sentence sounds unnatural in normal Portuguese:

• Arquivo já está no computador
• Teclado e mouse estão ao lado de impressora

That kind of omission might happen in:

• labels
• headlines
• notes
• highly telegraphic speech

But for ordinary sentences, keep the articles.

Nouns in Portuguese have grammatical gender, and impressora is a feminine noun:

• a impressora

That is why related words must match it:

• da impressora = de + a impressora

You simply need to learn the gender with the noun.

Examples:

• o computador
• o teclado
• a impressora

Gender in Portuguese does not always follow natural logic; it is part of the word.

A natural Brazilian pronunciation would reduce some unstressed vowels and link words together smoothly.

A rough pronunciation guide:

O arquivo já está no computador, mas o teclado e o mouse estão ao lado da impressora.

Approximate sound: u ar-KEE-vu zhah es-TAH nu com-pu-ta-DOR, maz u te-CLA-du i u MAU-si es-TOWN au LA-du da im-pres-SO-ra

A few helpful notes:

• o often sounds like u in unstressed position
• de and e can sound lighter in fast speech
• estão has a nasal ending
• mas often sounds like maz before a vowel or in connected speech

This is only an approximation, but it can help you hear the rhythm better.