Há quatro pessoas aqui.

Here, há means there is / there are in the sense of existence.

So Há quatro pessoas aqui literally means something like There are four people here.

In this use, há comes from the verb haver, but you do not need to think of it as a normal have verb here. In Brazilian Portuguese, haver in this structure is mainly used to express that something exists or is present.

Examples:

• Há um problema. = There is a problem.
• Há muitas casas na rua. = There are many houses on the street.

Because haver used in the meaning of there is / there are is impersonal in Portuguese.

That means it stays in the singular, usually as há in the present tense, no matter whether what follows is singular or plural.

Compare:

• Há uma pessoa aqui. = There is one person here.
• Há quatro pessoas aqui. = There are four people here.
• Há muitos carros lá fora. = There are many cars outside.

So even with quatro pessoas, the verb does not change.

They can sound similar, but they are different words.

• há = a form of haver, meaning there is / there are or sometimes ago
• a = usually a preposition meaning to, at, or sometimes just part of other structures

Examples:

• Há quatro pessoas aqui. = There are four people here.
• Daqui a quatro dias. = In four days / four days from now.

The accent mark in há helps show that it is a different word.

The singular noun is pessoa = person.

Its plural is pessoas = people / persons.

This follows a very common Portuguese pattern:

• words ending in -a often make the plural with -s

So:

• pessoa → pessoas
• casa → casas
• mesa → mesas

Also, in Portuguese, pessoas is the normal everyday word where English often uses people.

Portuguese does have collective meanings, but the normal straightforward way to say four people is quatro pessoas.

The singular is:

• uma pessoa = one person

The plural is:

• duas pessoas
• três pessoas
• quatro pessoas

So in everyday Portuguese, pessoa/pessoas works very naturally where English uses person/people.

Both are possible.

• Há quatro pessoas aqui.
• Aqui há quatro pessoas.

The first one is very natural and neutral: it first says that something exists, then tells you what it is, then where.

The second puts more focus on aqui (here), as if contrasting this place with another place.

So:

• Há quatro pessoas aqui. = neutral, very common
• Aqui há quatro pessoas. = more emphasis on here

Yes. In spoken Brazilian Portuguese, tem is extremely common in this meaning.

So these can both mean There are four people here:

• Há quatro pessoas aqui.
• Tem quatro pessoas aqui.

Important difference:

• há is more formal, more traditional, and very common in writing
• tem is extremely common in everyday speech in Brazil

If you are learning standard grammar, it is good to know há well. If you are listening to Brazilians speak, you will very often hear tem.

Yes, that is grammatically correct.

• Há quatro pessoas aqui.
• Existem quatro pessoas aqui.

Both mean roughly There are four people here.

But there is a small difference in feel:

• há is the most standard existential structure
• existem can sound a little more explicit or formal, depending on context

Also note:

• há stays singular
• existem agrees with the plural noun

So:

• Há quatro pessoas aqui.
• Existem quatro pessoas aqui.

But:

• Há uma pessoa aqui.
• Existe uma pessoa aqui.

Yes, aqui usually means here.

It refers to a place close to the speaker.

Examples:

• Estou aqui. = I am here.
• Há quatro pessoas aqui. = There are four people here.

A useful comparison:

• aqui = here
• ali = there, over there
• lá = there, farther away / there in general

So you could also say:

• Há quatro pessoas ali. = There are four people there.
• Há quatro pessoas lá. = There are four people there.

In Brazilian Portuguese, há is usually pronounced like ah, with an open a sound.

Very roughly for an English speaker:

• há ≈ ah

The h is silent in Portuguese here.

So the sentence sounds roughly like:

• ah KWA-troo peh-SO-ahs ah-KEE

That is only an approximation, but it can help at first.

No. In this sentence, you do not use an article.

So:

• Há quatro pessoas aqui. = correct

Not:

• Há as quatro pessoas aqui. unless you mean something specific like the four people are here, which is a different idea

When you are just stating that some quantity exists, Portuguese normally does not use an article before the noun:

• Há dois carros na rua.
• Há muita gente aqui.
• Há quatro pessoas aqui.

Yes. Há can also mean ago in time expressions.

Examples:

• Há dois dias = two days ago
• Há muito tempo = a long time ago

You understand the meaning from context.

Compare:

• Há quatro pessoas aqui. = There are four people here.
  Here, há introduces something that exists.
• Cheguei há quatro dias. = I arrived four days ago.
  Here, há is part of a time expression.

So the word is the same, but the structure tells you the meaning.

Há quatro pessoas aqui sounds neutral to somewhat formal.

It is completely correct and natural, especially in writing, announcements, descriptions, or careful speech.

In informal spoken Brazilian Portuguese, many speakers would more naturally say:

• Tem quatro pessoas aqui.

So a useful way to think about it is:

• há = standard, correct, common in writing, somewhat more formal
• tem = very common in everyday spoken Brazilian Portuguese

Both are important to understand.