Meu pulso dói quando eu uso o mouse o dia todo.

Here, pulso means wrist.

In Portuguese, pulso can mean both:

• wrist
• pulse (the heartbeat you feel in your wrist or neck)

Usually, context makes it clear. In a sentence about using a computer mouse and feeling pain, pulso is understood as wrist.

A related word is punho, which can also mean wrist, but pulso is very common in pain/injury contexts like repetitive strain.

Doer is the infinitive, meaning to hurt.

In the sentence, the verb is conjugated:

• doer = to hurt
• dói = hurts

So Meu pulso dói means My wrist hurts.

It is dói because the subject is meu pulso, which is third person singular.

Very roughly:

• eu doo
• você/ele/ela dói
• nós doemos
• eles/elas doem

The form dói also has the accent because of its pronunciation.

Portuguese often expresses pain by making the body part the subject:

• Meu pulso dói. = My wrist hurts.
• Minha cabeça dói. = My head hurts.
• Meu joelho dói. = My knee hurts.

This is a very normal structure in Portuguese.

Another common way is:

• Estou com dor no pulso. = I have pain in my wrist / My wrist hurts.

So the sentence given is completely natural.

Yes, eu can be omitted.

Portuguese often drops subject pronouns because the verb form already shows the person:

• quando eu uso o mouse o dia todo
• quando uso o mouse o dia todo

Both are correct.

Including eu can make the sentence a little clearer or slightly more emphatic, but it is not required here.

In Portuguese, articles are used more often than in English.

So when talking about the computer device in a normal, specific, everyday way, Brazilians usually say:

• usar o mouse
• pegar o mouse
• clicar no mouse

Using mouse without the article is possible in some contexts, but o mouse sounds more natural in a sentence like this.

Also, mouse is masculine in Brazilian Portuguese, so it takes o:

• o mouse

Yes. Mouse is the standard everyday word in Brazilian Portuguese for the computer device.

People do not normally translate it as rato.

So these are natural:

• o mouse
• clicar com o mouse
• usar o mouse

O dia todo means all day or the whole day long.

So:

• uso o mouse o dia todo = I use the mouse all day

This expression refers to duration.

A useful comparison:

• o dia todo = all day long
• todo dia = every day

So:

• Eu trabalho no computador o dia todo. = I work on the computer all day.
• Eu trabalho no computador todo dia. = I work on the computer every day.

That distinction is very important.

In Brazilian Portuguese, o dia todo is the most natural way to say all day long.

• o dia todo = all day
• a noite toda = all night
• a semana toda = the whole week

By contrast, todo dia usually means every day.

You may also hear todo o dia, but in modern Brazilian usage, learners should usually remember:

• o dia todo = all day
• todo dia = every day

That will keep your meaning clear.

Because the sentence describes a general situation or habitual pattern:

• when I use the mouse all day, my wrist hurts

Portuguese often uses the simple present for this kind of repeated or usual result.

It is not necessarily describing only this exact moment. It can mean something like:

• This happens whenever I use the mouse all day.

If you wanted to stress that it is happening right now, you could say:

• Meu pulso está doendo quando uso o mouse o dia todo.
• or more naturally, Meu pulso está doendo porque usei/fiquei usando o mouse o dia todo.

But for a general statement, dói is perfect.

Yes, but the meaning changes slightly.

• Meu pulso dói = My wrist hurts / My wrist tends to hurt.
• Meu pulso está doendo = My wrist is hurting.

So:

• dói is more general, habitual, or neutral
• está doendo emphasizes an ongoing pain right now

In your sentence, dói works very well because it describes what happens when you use the mouse all day.

Yes, you can absolutely say that.

Both are natural:

• Meu pulso dói quando eu uso o mouse o dia todo.
• Quando eu uso o mouse o dia todo, meu pulso dói.

The meaning is the same. The difference is mostly about emphasis:

• starting with Meu pulso dói... emphasizes the pain
• starting with Quando eu uso... emphasizes the condition/situation

Dói is pronounced roughly like DOY, with the stress on that syllable.

The accent in dói helps show the correct stress and vowel quality. For learners, the important thing is to pronounce it as one stressed syllable:

• dói

Compare:

• doi without an accent would not be the normal spelling here
• dói is the correct form

So say:

• Meu pulso dói → roughly meh-ooh POOL-so DOY

Yes, it is natural and understandable.

A Brazilian would easily say or understand:

• Meu pulso dói quando eu uso o mouse o dia todo.

Some other natural alternatives are:

• Meu pulso dói quando passo o dia todo usando o mouse.
• Fico com dor no pulso quando uso o mouse o dia todo.
• Meu pulso começa a doer quando uso o mouse o dia todo.

But the original sentence is already perfectly good Portuguese.