A torcida começou a vaiar o árbitro.

Torcida usually means the fans, the crowd of supporters, or a fan base, especially in sports.

In this sentence, a torcida is a collective noun: it refers to a group of people, but grammatically it is singular.

So even though many people are involved, Portuguese treats a torcida as one group:

• A torcida começou... = The crowd/fans started...

A more individual way to say it would be:

• Os torcedores começaram a vaiar o árbitro. = The fans started booing the referee.

Portuguese uses definite articles much more often than English.

So a torcida literally means the crowd / the fans. In English, we sometimes drop the, but in Portuguese it is very normal to include it.

Here:

• a = the (feminine singular)
• torcida = crowd of supporters / fans

So A torcida começou... is the natural way to say The crowd started...

Because the subject is a torcida, and torcida is grammatically singular.

Even though it refers to many people, Portuguese matches the verb with the grammatical form of the noun:

• A torcida começou... = singular
• Os torcedores começaram... = plural

Compare:

• A equipe venceu. = The team won.
• Os jogadores venceram. = The players won.

This is very similar to how English can say The team is... in some contexts.

In começou a vaiar, the a is part of the verb pattern:

• começar a + infinitive = to start/begin to do something

So:

• começou a vaiar = started to boo

This a is not the feminine article a meaning the. It is a preposition required by começar in this structure.

Other examples:

• Comecei a estudar. = I started to study.
• Ela começou a rir. = She started to laugh.

In standard Portuguese, no. The normal structure is:

• começar a + infinitive

So the correct form is:

• A torcida começou a vaiar o árbitro.

Without a, it sounds ungrammatical to most speakers.

Vaiar means to boo.

Yes, it is a common verb, especially in sports, politics, concerts, and public events.

Examples:

• O público vaiou o cantor. = The audience booed the singer.
• Os torcedores vaiaram o time. = The fans booed the team.

Related noun:

• vaia = booing / jeer
• levar vaia = to get booed

So in your sentence:

• começou a vaiar = started booing

Again, Portuguese often uses the definite article where English might or might not.

So:

• o árbitro = the referee

In this sentence, the referee is a specific person in the situation, so using o is natural.

You could think of the structure as:

• vaiar o árbitro = to boo the referee

Yes, árbitro here is masculine, which is why it takes:

• o árbitro

If the referee is female, you would normally say:

• a árbitra

So the sentence could become:

• A torcida começou a vaiar a árbitra.
  = The crowd started booing the female referee.

Notice that both the noun and article change:

• o árbitro = male referee
• a árbitra = female referee

Because Portuguese does not use the Spanish-style personal a before direct objects.

In this sentence:

• o árbitro is the direct object of vaiar

So Portuguese simply says:

• vaiar o árbitro

not something like Spanish a el árbitro.

This is helpful for English speakers because the structure is more straightforward:

• verb + direct object

Examples:

• vi o professor = I saw the teacher
• cumprimentei a médica = I greeted the doctor
• vaiaram o árbitro = they booed the referee

Começou is the pretérito perfeito (simple past / preterite) of começar.

It means the action started at a particular moment in the past.

So:

• começou = started / began

Full breakdown:

• eu comecei = I started
• você/ele/ela começou = you/he/she started
• nós começamos = we started
• eles/elas começaram = they started

In your sentence:

• A torcida começou a vaiar o árbitro.
• The crowd started booing the referee.

Yes, both words are worth noticing.

• vaiar is roughly vai-AR

  • The stress is on the last syllable.
  • The beginning vai sounds like English vie.

• árbitro is stressed on the first syllable:

  • AR-bi-tro
  • That is why it has an accent mark: á

So the sentence sounds roughly like:

• A tor-SEE-da co-me-SOW a vai-AR o AR-bi-tro

The exact Brazilian pronunciation will vary a bit by region, but the stress pattern stays the same.

Yes, but the meaning or style changes slightly.

• A torcida começou a vaiar o árbitro.

  • The crowd started to boo the referee.
  • Most neutral and direct.

• A torcida passou a vaiar o árbitro.

  • The crowd began to boo / came to start booing the referee.
  • Suggests a change in behavior or a new phase.

• A torcida começou vaiando o árbitro.

  • More like The crowd began by booing the referee
  • This can suggest that booing was the first action in a sequence.

For a learner, começar a + infinitive is the safest and most standard pattern to use.