Na segunda-feira, eu vou trabalhar de manhã e descansar à tarde.

Na segunda-feira means on Monday.

• na = em + a
• segunda-feira = Monday

In Portuguese, days of the week often use em with the definite article, so na segunda-feira literally feels like in/on the Monday.

You may also hear just segunda-feira without na, especially in more casual speech, but na segunda-feira is very common and completely natural.

In standard Portuguese, the weekday is called segunda-feira.

Brazilian weekdays are:

• segunda-feira = Monday
• terça-feira = Tuesday
• quarta-feira = Wednesday
• quinta-feira = Thursday
• sexta-feira = Friday

In casual speech, Brazilians often shorten them:

• segunda
• terça
• quarta, etc.

So both exist, but segunda-feira is the full form.

Na is a contraction of:

• em = in, on, at
• a = the

So:

• em + a = na

This kind of contraction is very common in Portuguese:

• em + o = no
• em + os = nos
• em + as = nas

Here, na segunda-feira is the natural way to say on Monday.

The comma separates the time expression from the main part of the sentence.

So:

• Na segunda-feira, eu vou trabalhar...

This is similar to English sentences like:

• On Monday, I’m going to work...

The comma is common and helps readability, especially when a sentence begins with a time phrase. In informal writing, some people may omit it, but using it here is good style.

Yes, eu can be omitted.

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

• eu vou
• você vai
• nós vamos

So this sentence could also be:

• Na segunda-feira, vou trabalhar de manhã e descansar à tarde.

That is perfectly natural.

The speaker may include eu for:

• clarity
• emphasis
• contrast

So eu is not required, but it is not wrong at all.

Vou trabalhar is a very common way to express the future in Brazilian Portuguese.

It is formed with:

• ir in the present tense: vou
• plus an infinitive: trabalhar

So:

• vou trabalhar = I am going to work / I will work
• vou descansar = I am going to rest / I will rest

This structure is extremely common in everyday Brazilian Portuguese and often sounds more natural than the simple future.

For comparison:

• Eu trabalharei = I will work
• Eu vou trabalhar = I’m going to work / I will work

Both are correct, but vou trabalhar is much more common in conversation.

Because Portuguese, like English, often avoids repeating the same verb when it is understood.

So:

• eu vou trabalhar de manhã e descansar à tarde

means:

• eu vou trabalhar de manhã e vou descansar à tarde

The second vou is omitted because it is already understood from the first part.

Both versions are correct, but the shorter version sounds smoother and more natural here.

They are in the infinitive because they come after vou, which is part of the future construction ir + infinitive.

So:

• vou trabalhar
• vou descansar

This is the same pattern as:

• vou estudar
• vou comer
• vou sair

After vou, the next verb normally stays in the infinitive.

These are fixed time expressions in Portuguese, and they do not all follow the same pattern.

Common expressions are:

• de manhã = in the morning
• à tarde = in the afternoon
• à noite = at night / in the evening

So you usually just learn them as chunks.

A useful pattern is:

• de manhã
• à tarde
• à noite

Even though English uses in for both in the morning and in the afternoon, Portuguese uses different prepositions in these standard expressions.

The à has a grave accent, and this usually shows crase, which is the contraction of:

• a
  • a

In many cases, it happens when a preposition a combines with a feminine article a.

So:

• à tarde
• à noite

These are standard expressions.

This accent is different from the acute accent in words like á. Here, à specifically signals this contraction.

For a beginner, the easiest approach is simply to memorize:

• à tarde
• à noite

as whole expressions.

Yes, but there are differences.

• de manhã is very common and standard.
• pela manhã is also common and can sound a little more explicit or formal in some contexts.
• à tarde is the most standard expression for in the afternoon.
• de tarde is heard in Brazil and is natural in many regions, but à tarde is the safer standard form for learners.

So for a learner, these are the best choices:

• de manhã
• à tarde
• à noite

Most naturally, it describes a future plan for Monday.

Because of vou + infinitive, the sentence usually means the speaker is saying what they are going to do.

So it sounds like:

• On Monday, I’m going to work in the morning and rest in the afternoon.

If you wanted to describe a habitual routine, Portuguese would more often use the present tense, for example:

• Na segunda-feira, trabalho de manhã e descanso à tarde.

That sounds more like a regular schedule or habitual action.

Yes, somewhat.

The given sentence is very natural:

• Na segunda-feira, eu vou trabalhar de manhã e descansar à tarde.

But Portuguese allows some variation, for example:

• Eu vou trabalhar de manhã e descansar à tarde na segunda-feira.
• Eu, na segunda-feira, vou trabalhar de manhã e descansar à tarde.

Still, the original version is excellent because it introduces the time first, which is very natural when setting the scene.

Not in the same way English does.

These are set Portuguese expressions:

• de manhã
• à tarde

You should not try to translate them word-for-word from English. Even though English says in the morning and in the afternoon, Portuguese uses its own idiomatic patterns.

So the best approach is to learn the full expressions, not analyze them too literally.

Yes.

Eu vou trabalhar can often correspond to:

• I’m going to work
• I will work

Which English version fits best depends on context.

In everyday Brazilian Portuguese, ir + infinitive is a normal future form, so it does not always sound as literal as English going to. Very often it simply means a future action.

So in practice:

• eu vou trabalhar = I’ll work / I’m going to work

Both are possible translations.