Learn Hardcore Portuguese (Portugal): A Maria prefere séries policiais, enquanto o irmão gosta mais de mistérios antigos. - Maria prefers crime series, while her brother likes old mysteries more.

It doesn’t usually change the meaning; it’s more of a stylistic/colloquial feature of European Portuguese. You will hear it a lot in everyday speech and also see it in writing.

In Brazilian Portuguese, using the article before names is less common and can sound regional or informal, but in Portugal it’s standard and very natural.

You could also say just “Maria prefere séries policiais…”, but “A Maria” is perfectly normal and often sounds more natural in European Portuguese.

How does “o irmão” here mean “her brother”? There’s no word for “her”.

Portuguese often uses the definite article + family member to indicate a known relation, and the context tells you whose relative it is:

A Maria prefere séries policiais, enquanto o irmão gosta…
Literally: “Maria prefers police series, while the brother likes…”

Because we’ve just mentioned Maria, o irmão is naturally understood as her brother.

You could make it more explicit with:

…enquanto o irmão dela gosta… = while her brother likes…
…enquanto o seu irmão gosta… (European Portuguese: often sounds a bit more formal/written)

But in this kind of short context, o irmão alone is very normal and not ambiguous.

What exactly does “enquanto” mean here: “enquanto o irmão gosta mais de…”? Is it “while” or “whereas”?

Enquanto can mean both “while” (time) and “whereas” (contrast).
Here it’s clearly expressing contrast:

A Maria prefere séries policiais, enquanto o irmão gosta mais de mistérios antigos.
= Maria prefers crime series, whereas her brother likes old mysteries more.

It doesn’t have to mean both things happening at the same time; it’s more about comparing preferences.

You could also say:

…enquanto que o irmão gosta… – very similar, slightly more explicit contrast.
…ao passo que o irmão gosta… – more formal, also “whereas”.

Why is there a comma before “enquanto”?

The sentence has two clauses:

A Maria prefere séries policiais,
enquanto o irmão gosta mais de mistérios antigos.

They are joined by enquanto, and they form a contrast. In Portuguese, it’s common to put a comma before a conjunction that introduces a new clause, especially when:

the clauses are relatively independent, and
the conjunction marks a contrast (like enquanto, mas, porém etc.).

So the comma here is normal and correct: it separates Maria’s preference from the brother’s preference.

Why is it “gosta mais de mistérios antigos” and not just “gosta mistérios antigos”?

In Portuguese, the verb gostar needs the preposition “de” before what you like:

gostar de algo = to like something

So we get:

gosta de mistérios antigos = he likes old mysteries
gosta mais de mistérios antigos = he likes old mysteries more

Leaving out de (gosta mistérios antigos) is grammatically wrong.

The structure is:

gostar (mais) de + [noun / verb in infinitive]
- gosto de música – I like music
- gosto de ler – I like reading
- gosto mais de café – I like coffee more

What is the role of “mais” in “gosta mais de mistérios antigos”?

Mais means “more”. It strengthens gostar de:

gosta de mistérios antigos = he likes old mysteries
gosta mais de mistérios antigos = he likes old mysteries more / he prefers old mysteries

So mais adds a comparative sense (a stronger preference) rather than just “he likes them”. Without mais, it would sound more neutral:

O irmão gosta de mistérios antigos. = The brother likes old mysteries (not necessarily more than other things).

What’s the difference between “prefere” and “gosta mais de” in this sentence?

Both express preference, but they work slightly differently:

prefere séries policiais
- literally: “prefers crime series”
- very direct, neutral way to say what someone prefers
gosta mais de mistérios antigos
- literally: “likes old mysteries more”
- uses gostar
  - mais to express a stronger liking / preference

You could rephrase either part with the other structure:

A Maria gosta mais de séries policiais.
O irmão prefere mistérios antigos.

All of these would be natural. The original sentence just uses two different but common ways of talking about preferences.

Why is it “séries policiais” and not “séries de polícia”?

Both are possible, but there’s a nuance:

séries policiais
- very common and natural expression
- literally “police series” / “crime series”
- policiais is an adjective (“police / crime-related”), agreeing in gender and number with séries (feminine plural → policiais).
séries de polícia
- literally “series of police”
- grammatically fine, but much less idiomatic for the TV/film genre
- could sound like series about the police as an institution, not necessarily the “crime drama” genre.

For the genre like CSI, Luther, Line of Duty, séries policiais is the standard phrase.

Why is it “mistérios antigos” and not “antigos mistérios”? Does the adjective order matter?

Yes, the position of adjectives in Portuguese can slightly affect the nuance:

mistérios antigos (noun + adjective)
- the neutral, default order
- means “old mysteries” in a descriptive sense (mysteries that are old in time).
antigos mistérios (adjective + noun)
- can sometimes have a more figurative or emotional feel, or highlight “ancient/longstanding” as a more intrinsic quality
- often used in set phrases or stylistic/literary contexts.

In this everyday context (talking about what someone likes to watch/read), mistérios antigos is the most natural and unmarked choice: just “old mysteries”.

Why are the adjectives “policiais” and “antigos” after the nouns, and how do they agree?

Adjectives in Portuguese usually follow the noun:

séries policiais
- séries: feminine plural
- policiais: plural form of policial (adjective), agrees in number (plural) but not in gender (it has the same form for masculine and feminine in the plural)
mistérios antigos
- mistérios: masculine plural
- antigos: masculine plural form of antigo (old), agrees in gender and number

General rules visible here:

Adjective normally comes after the noun (especially in neutral descriptions).
It must agree in number, and usually in gender, with the noun:
- mistério antigo (singular)
- mistérios antigos (plural)
- série policial / séries policiais

Why isn’t there a subject pronoun like “Ela” or “Ele” in the sentence?

Portuguese is a pro-drop language: subject pronouns are often omitted because the verb ending already shows the person:

(A Maria) prefere
- prefere can only be he/she/you-formal (3rd person singular)
- the subject A Maria is explicitly there, so you don’t need Ela.
(O irmão) gosta mais de…
- again, gosta = he/she/you-formal likes
- we already have o irmão as the subject.

You can add pronouns for emphasis or contrast:

Ela, a Maria, prefere séries policiais, mas ele gosta mais de mistérios antigos.
(She, Maria, prefers…, but he likes… more.)

But it’s not required, and in neutral statements like this you usually drop them.

Is the Portuguese present tense “prefere / gosta” used like the English “likes / prefers” for general preferences?

Yes. The presente do indicativo in Portuguese is used for:

general truths and habits
stable preferences

So:

A Maria prefere séries policiais…
…o irmão gosta mais de mistérios antigos.

both mean:

“Maria prefers crime series, and her brother likes old mysteries more.”

This is parallel to the English simple present (prefers / likes) when you talk about what someone generally likes, not about a one-time action.

Could we say “gosta mais dos mistérios antigos” instead of “de mistérios antigos”?

Yes, but it changes the nuance slightly:

gosta mais de mistérios antigos
- no article → more general: he likes old mysteries as a type/genre.
- like saying “He likes old mysteries (in general).”
gosta mais dos mistérios antigos
- dos = de + os (of the) → more specific: “the old mysteries”
- suggests a particular group of mysteries already known from context (e.g. those old mysteries we talked about).

In your sentence, the idea is general taste, so de mistérios antigos (no article) is the better, more natural choice.