A polícia vigia o bairro à noite.

The police watch the neighbourhood at night.

Breakdown of A polícia vigia o bairro à noite.

• a noite: the night
• o bairro: the neighbourhood
• a polícia: the police
• à: at
• vigiar: to monitor

Questions & Answers about A polícia vigia o bairro à noite.

Why is it a polícia and not o polícia or as polícias here?

Polícia has two main uses:

1. The institution “the police”

   • In this meaning, Portuguese uses feminine singular: a polícia.
   • Even though it refers to many people, grammatically it is one institution, so:
     • a polícia vigia (singular verb)

2. An individual police officer

   • o polícia = one male police officer
   • a polícia = one female police officer
   • os / as polícias = police officers (plural, people)

In your sentence, a polícia clearly means the police as an institution, so it is feminine singular, and vigia agrees with that.

If a polícia refers to many people, why is the verb vigia (singular) and not vigiam?

Because a polícia is a collective noun treated as singular in grammar.

• Subject: a polícia → 3rd person singular
• Verb: vigiar (to watch, keep under surveillance)
  
  • 3rd person singular: ele/ela vigia

So:

• A polícia vigia o bairro. ✅
• A polícia vigiam o bairro. ❌ (ungrammatical)

If you explicitly talked about the officers as individuals, you’d use a plural subject:

• Os polícias vigiam o bairro. = The (police) officers watch the neighbourhood.

What tense and aspect does vigia express? Is it “watches” or “is watching”?

Vigia is present indicative, 3rd person singular of vigiar.

Portuguese present tense can cover what English expresses with both:

• “watches” (habitual)
• “is watching” (right now)

Your sentence A polícia vigia o bairro à noite is most naturally understood as habitual:

• The police watch the neighbourhood at night / at nighttime.

If you wanted to emphasise “right now, tonight”, you’d normally add something like hoje (today) or esta noite (tonight):

• Hoje à noite, a polícia vigia o bairro. = Tonight, the police are watching the neighbourhood.

What nuance does the verb vigiar have? Could I say patrulhar or guardar instead?

Vigiar means to watch, keep under surveillance, keep an eye on, often with attention and some suspicion or protection.

• A polícia vigia o bairro.
  → The police keep the neighbourhood under watch / under surveillance.

Alternatives:

• patrulhar = to patrol

  • A polícia patrulha o bairro à noite.
    → Emphasis on moving around the area in patrols.

• guardar = to guard, to stand watch over (often more static, protecting an entry, building, etc.)

  • A polícia guarda a entrada do bairro.
    → Emphasis on guarding a specific point.

So vigiar focuses on surveillance, patrulhar on moving patrols, guardar on guarding/protecting a place.

Why is it o bairro (with masculine article o)?

In Portuguese, every noun has a grammatical gender.
Bairro happens to be masculine, so it takes masculine forms:

• o bairro = the neighbourhood
• um bairro = a neighbourhood
• os bairros = the neighbourhoods

You simply have to learn the gender of each noun; there’s no reliable rule from meaning alone. Dictionaries usually mark it as (sm) = substantivo masculino.

Why o bairro and not no bairro? What’s the difference between vigiar o bairro and vigiar no bairro?

The difference is between object and location:

• vigiar o bairro
  → The neighbourhood itself is what they are watching (direct object).

• vigiar no bairro
  → They are watching in the neighbourhood, but what they’re watching is not specified.

So:

• A polícia vigia o bairro à noite.
  → The police keep the neighbourhood under surveillance at night.

• A polícia vigia no bairro à noite.
  → The police keep watch in the neighbourhood at night (maybe watching certain people, houses, cars, etc., but the object isn’t stated).

In your sentence, the intended meaning is that the neighbourhood as a whole is under surveillance, so o bairro is the direct object.

What exactly does bairro mean in European Portuguese? Is it always “neighbourhood”?

In European Portuguese, bairro usually means:

• neighbourhood / district / quarter (a part of a city or town with its own identity)

Depending on context, it can also mean:

• a housing estate or specific residential area
• a socially marked area, e.g. bairro social (social housing estate).

In most everyday urban contexts, you can safely think of bairro as “neighbourhood”.

What does à noite mean exactly, and how is à formed? How is it different from de noite?

À noite means “at night / in the evening/nighttime (in general)”.

Grammatically, à is a contraction:

• a (preposition “to/at”)
  
  • a (feminine singular definite article “the”)
    = à

So à noite literally is “at the night”, but it functions like English “at night”.

Difference from de noite:

• à noite and de noite both often mean “at night / by night”.
• à noite is slightly more neutral/standard.
• de noite can feel a bit more colloquial or descriptive (“during the night”), but in many contexts they’re interchangeable.

Examples:

• Trabalho à noite. / Trabalho de noite. = I work at night.

Can the time expression à noite move in the sentence? For example, is À noite, a polícia vigia o bairro also correct?

Yes, time expressions are quite flexible in Portuguese. All of these are correct, with only slight differences in emphasis:

• A polícia vigia o bairro à noite.
• À noite, a polícia vigia o bairro. (stronger emphasis on “at night”)
• A polícia, à noite, vigia o bairro. (more marked, often written style)

The basic meaning stays the same. The original word order is the most neutral.