A reunião começa às oito.

A is the feminine singular definite article, meaning the.

• reunião = meeting
• a reunião = the meeting

In Portuguese, articles are used more often than in English, so leaving out a can sound less natural in many contexts.

Nouns in Portuguese have grammatical gender, and reunião is a feminine noun.

That is why it takes:

• a reunião = the meeting
• not o reunião

There is not always a logical reason for gender, so this is something you usually memorize with the noun: a reunião.

Começa is the third-person singular form of the verb começar, which means to begin or to start.

So:

• começar = to begin / to start
• começa = begins / starts

In this sentence, a reunião is singular, so the verb is singular too:

• A reunião começa = The meeting starts

Portuguese often does not need an explicit subject pronoun when the subject is already stated or clear.

Here, the subject is a reunião, so there is no need to say it:

• A reunião começa... = The meeting starts...

Unlike English, Portuguese does not usually require a separate subject like it after the noun.

Às is used to express a specific clock time.

• às oito = at eight
• às nove = at nine
• às dez = at ten

So the structure is:

• começar às + time

This is the normal way to say at a certain hour in Portuguese.

Às is a contraction of:

• a = the preposition at / to
• as = the feminine plural definite article the

So:

• a + as = às

This happens because Portuguese treats clock times like the eight hours, the nine hours, etc.

That is why you say:

• à uma = at one
• às duas = at two
• às oito = at eight

The accent in às is a grave accent and shows a contraction called crase.

Here it marks that:

• the preposition a
• combines with the article as

So:

• a + as = às

This accent is important because it tells you this is not just as by itself.

Both are possible.

• A reunião começa às oito.
• A reunião começa às oito horas.

In everyday speech, Portuguese often drops horas when the meaning is obvious. Saying just às oito is very natural.

A helpful Brazil Portuguese approximation is:

• reh-oo-nee-OW̃

A few things to notice:

• the stress falls on the last syllable: -ão
• ão is nasal
• reu is pronounced as one flowing part, not like separate English syllables

The nasal ending in -ão is very common in Portuguese, so this is a useful pattern to practice.

A rough pronunciation guide is:

• a hey-oo-nee-OW̃ koh-MEH-sah az OY-too

A few notes:

• reunião has stress on -ão
• começa has stress on me
• às sounds like az before a vowel sound in connected speech
• oito in Brazil is roughly OY-too

This is only an approximation, but it can help at the beginning.

Yes, but começa is more common and natural in everyday conversation.

• A reunião começa às oito. = very natural
• A reunião inicia às oito. = understandable, but often sounds more formal or administrative

In many everyday situations, começar is the safer choice.

Yes, but A reunião começa às oito is the most neutral and standard order.

Other possible orders include:

• Às oito, a reunião começa.
• Começa às oito, a reunião. — possible in some contexts, but less neutral

For a learner, the basic pattern is best:

• [subject] + [verb] + [time]
• A reunião começa às oito.

In Brazilian Portuguese, you can often make it a question just by using intonation:

• A reunião começa às oito?

You could also ask more explicitly:

• A reunião começa às oito mesmo? = Does the meeting really start at eight?
• A que horas a reunião começa? = What time does the meeting start?

Portuguese usually does not need do/does like English does.

No. The correct spelling is começa.

The ç is called cedilha. It shows that the c is pronounced like s before a, o, or u.

So:

• começa sounds like ko-MEH-sa
• without the cedilla, comeca would not be standard Portuguese spelling

A very useful pattern is:

• [event] + começa + às + [time]

Examples:

• A aula começa às nove. = The class starts at nine.
• O filme começa às sete. = The movie starts at seven.
• O jogo começa às três. = The game starts at three.

This makes A reunião começa às oito a great model sentence to reuse.