Learn Hardcore Portuguese (Brazil): Minha irmã prefere correr à noite, quando a cidade está mais vazia. - My sister prefers to run at night, when the city is emptier.

In Portuguese, after verbs like preferir (to prefer), querer (to want), poder (can), etc., you normally use the infinitive form of the second verb:

Minha irmã prefere correr. = My sister prefers to run.
Eu quero viajar. = I want to travel.

Using correndo would sound more like English “She prefers running” in a general sense, but in Portuguese that structure is not natural after preferir. You stick with the infinitive: prefere correr, not prefere correndo.

What does the accent in à noite mean? Why not just a noite?

The à here is a case of crase: the combination of the preposition a (to/at) + the feminine article a (the), written with a grave accent: a + a → à.

à noite literally = at the night → idiomatically at night

If you wrote a noite (without the accent), it would usually be read as the night as a subject or object, not as “at night”:

A noite está fria. = The night is cold.

So, to say at night, you normally write à noite with crase.

Can I say de noite instead of à noite? Is there any difference?

Yes, you can say de noite. Both are common and correct:

à noite = at night
de noite = at night

Differences:

à noite is a bit more neutral/standard, often used in writing.
de noite feels slightly more informal/colloquial in many regions.

In everyday speech, Brazilians use both a lot. Your sentence would still be natural as:

Minha irmã prefere correr de noite, quando a cidade está mais vazia.

Why is it quando a cidade está mais vazia and not é mais vazia?

Portuguese uses estar for temporary or changing situations and ser for more permanent characteristics.

Here, the city being empty is a temporary condition (only at night), so estar is used:

A cidade está mais vazia. = The city is emptier (right now / at that time).

If you said a cidade é mais vazia, it would sound like a permanent trait, which doesn’t fit well here.

Why do we say a cidade and not just cidade?

In Portuguese, the definite article (o, a, os, as) is used more often than “the” in English.

a cidade = the city

In this sentence, a cidade refers to “the city” that both speaker and listener already know (their city). Leaving out the article (quando cidade está mais vazia) would be incorrect here.

Also, cidade is a feminine noun, so it takes a (feminine singular) rather than o.

Why is vazia feminine? Shouldn’t adjectives be invariable, like in English?

In Portuguese, adjectives agree in gender and number with the noun they describe.

cidade is feminine singular.
The adjective must also be feminine singular: vazia.

Examples:

A cidade está vazia. (feminine singular)
As cidades estão vazias. (feminine plural)
O parque está vazio. (masculine singular)
Os parques estão vazios. (masculine plural)

So mais vazia (“emptier”) matches a cidade in gender and number.

What does mais vazia mean exactly? Why use mais?

mais is “more”, and vazia is “empty”, so:

mais vazia = more empty / emptier

Portuguese often forms the comparative with mais + adjective:

mais rápido = faster
mais bonito = more beautiful
mais vazio / mais vazia = emptier

There is no separate single-word comparative like English “emptier”; instead you say mais vazia.

Why is there a comma before quando?

The comma separates the main clause from the subordinate clause:

Main clause: Minha irmã prefere correr à noite
Subordinate clause (time/condition): quando a cidade está mais vazia

In Portuguese, it is normal (and often required) to use a comma when a dependent clause introduced by words like quando, porque, se, embora follows the main clause.

So the comma here is standard punctuation and makes the sentence clearer.

Could I say Minha irmã prefere correr quando a cidade está mais vazia à noite?

That word order is grammatically possible, but it sounds less natural and a bit confusing, because à noite would seem to modify está mais vazia instead of correr.

Native speakers are more likely to keep à noite close to correr, as in the original:

Minha irmã prefere correr à noite, quando a cidade está mais vazia.

This makes it clear that running at night is what she prefers, and the second part explains why (because the city is emptier).

Why is it Minha irmã and not A minha irmã? I’ve seen both.

Both forms exist, but there is a regional difference:

In Brazilian Portuguese, with close family members, it’s very common (and more natural) to say:
- Minha irmã, meu pai, minha mãe, etc.
In European Portuguese, it’s very common to include the article:
- A minha irmã, o meu pai, a minha mãe, etc.

In Brazil, Minha irmã prefere correr à noite… is the most typical pattern.
You might still occasionally hear A minha irmã, but it’s less frequent in Brazilian Portuguese.

Why don’t we repeat the subject pronoun ela? Could I say Ela, minha irmã, prefere…?

Portuguese is a pro-drop language: subject pronouns (eu, tu, ele, ela, etc.) are often omitted when the verb ending already shows who the subject is.

Here, minha irmã is the subject, so there’s no need for ela:

Minha irmã prefere correr à noite… (natural)
Ela prefere correr à noite… (also correct, but now ela is the subject by itself)
Ela, minha irmã, prefere… sounds possible, but it adds a pause and emphasis, like clarifying “She, my sister, prefers…”—not needed in a simple, neutral sentence.

So the original form is the most straightforward and natural.

What’s the difference between prefere correr and something like costuma correr?

They express different ideas:

prefere correr à noite = she prefers to run at night
- Focus on preference: night vs morning/afternoon.
costuma correr à noite = she usually runs at night
- Focus on habit/frequency, not necessarily a preference.

So:

If you mean what she likes more, use prefere.
If you mean what she usually does, use costuma.