A corrida começa agora.

In Portuguese, a can be the feminine singular definite article, meaning the.

So:

• a corrida = the race

This can be confusing for English speakers because English a is an indefinite article, but in Portuguese the indefinite article would be uma.

So:

• a corrida = the race
• uma corrida = a race

Corrida is a feminine noun in Portuguese, so it takes feminine words with it, such as the article a.

This is grammatical gender, not biological gender. In other words, corrida is feminine because that is just how the noun is classified in Portuguese.

That is why you say:

• a corrida
• not o corrida

Começa is the 3rd person singular present tense form of the verb começar, which means to begin or to start.

The subject here is a corrida, which is singular, so the verb must also be singular:

• a corrida começa = the race starts / begins

A few present-tense forms of começar are:

• eu começo
• você / ele / ela começa
• nós começamos
• vocês / eles / elas começam

Portuguese, like English, often uses the simple present for events that are happening now or are scheduled to happen immediately.

So A corrida começa agora is very natural and can mean something like:

• The race starts now
• The race is starting now

It sounds like an announcement or a statement about an event beginning at this moment.

They both help with pronunciation.

• ç makes an s sound before a, o, or u
• the acute accent in começa shows the stressed syllable

So começa is pronounced roughly like:

• ko-MEH-sa

If it were written with a plain c before a, it would sound like k, which would be wrong here.

Agora usually means now.

In this sentence, it means at this moment or right now:

• A corrida começa agora = The race starts now

Depending on context, agora can sometimes be a little flexible, like English now, but here it clearly refers to the present moment.

Yes, it could.

The sentence A corrida começa agora follows a very normal word order:

• subject + verb + time expression

But Portuguese also allows other placements, especially for emphasis:

• Agora a corrida começa
• Agora começa a corrida

These are possible, but they can sound more marked or dramatic depending on context. The original version is the most neutral and straightforward.

Not always. Corrida can have different meanings depending on context.

In Brazilian Portuguese, common meanings include:

• race
• run
• sometimes a ride/trip, especially in taxi or app-driver contexts

In other varieties or contexts, it can also refer to a bullfight.

But in A corrida começa agora, the most natural reading is the race starts now.

Yes. All of these are possible, but they are slightly different.

• A corrida começa agora
  Neutral and very natural. Good for announcements and schedules.

• A corrida vai começar agora
  Emphasizes that it is about to begin.

• A corrida está começando agora
  Emphasizes that the beginning is happening right now, in progress.

So the original sentence is simple, natural, and very common.

A rough pronunciation guide is:

• a ko-HEE-da ko-MEH-sa a-GO-ra

A few notes:

• corrida has rr, which in Brazilian Portuguese is usually a strong guttural r sound
• começa is stressed on me
• agora is usually stressed on go

A more phonetic approximation is:

• a ko-REE-da ko-MEH-sa a-GO-ra

The exact r sound will vary by region, but the stress pattern stays the same.