A többi önkéntes is itt van.

A fairly literal breakdown is:

• a = the
• többi = the rest / the remaining / the other
• önkéntes = volunteer
• is = also / too
• itt = here
• van = is / are in the sense of is here / exists / is present

So the sentence is literally something like:

The rest of the volunteer also here is

In natural English: The other volunteers are here too or The rest of the volunteers are here too.

Because a többi usually refers to a specific remaining part of a known group.

So:

• a többi önkéntes = the rest of the volunteers / the other volunteers
• not just volunteers in general, but the ones left over from a group already understood in the conversation

Hungarian often uses the definite article here because the group is treated as identifiable.

Also, a is simply the short form of the definite article. Hungarian has:

• a before most consonant-initial words
• az before vowel-initial words

Since többi begins with a consonant, it is a többi.

Többi means the rest, the remaining ones, or the other ones from the same group.

In this sentence, it does not mean just any other volunteers in the world. It means the volunteers that belong to a group already being talked about.

For example, if some volunteers have already arrived, then:

A többi önkéntes is itt van.
= The rest of the volunteers are here too.

A useful comparison:

• másik = another / the other one
• többi = the rest / the others remaining

So többi is about what remains from a set.

Because after words like többi, Hungarian normally uses the singular noun form, even when the meaning is plural in English.

So Hungarian says:

• a többi önkéntes
  not
• a többi önkéntesek

This is similar to other Hungarian quantity-like structures, where English uses a plural noun but Hungarian often uses a singular form.

So even though the sentence refers to multiple volunteers, the noun itself stays singular after többi.

Because a többi önkéntes is treated grammatically as a singular collective expression.

So Hungarian says:

• A többi önkéntes itt van.

not usually:

• A többi önkéntes itt vannak.

Even though English translates this with a plural verb (are), Hungarian uses singular agreement here.

If you want a clearly plural subject, Hungarian often uses a different word:

• A többiek is itt vannak.
  = The others are here too.

So:

• a többi önkéntes → singular-style grammar
• a többiek → plural-style grammar

Is means also or too.

It comes after the word or phrase it belongs to. Here it follows the whole noun phrase:

• a többi önkéntes is = the other volunteers too

So the sentence means that besides someone else already being here, the other volunteers are here as well.

This is a very important point: Hungarian is is not the verb is from English. It is a small particle meaning also / too / even.

Compare:

• Péter is itt van. = Peter is here too.
• A többi önkéntes is itt van. = The other volunteers are here too.

That is a very common question.

Hungarian often omits the present-tense verb to be in sentences like:

• Ő önkéntes. = He/She is a volunteer.
• A ház nagy. = The house is big.

But with location or existence, Hungarian normally keeps van:

• Itt van. = He/She/It is here.
• A könyv az asztalon van. = The book is on the table.

So in A többi önkéntes is itt van, van is needed because the sentence is about being here, that is, location/presence.

Not completely. Hungarian word order is quite flexible, and it often changes according to topic, focus, and emphasis.

The sentence:

A többi önkéntes is itt van.

is a natural, neutral way to say it.

It roughly works like this:

• A többi önkéntes is = topic / what we are talking about
• itt van = what is being said about them

If you move things around, the emphasis can change. Hungarian does this much more freely than English, but not every rearrangement sounds equally natural in every context.

So for a learner, the safest point is:

• A többi önkéntes is itt van = normal, natural sentence

Yes. In English, both can work depending on context.

A többi önkéntes can be translated as:

• the other volunteers
• the rest of the volunteers
• the remaining volunteers

The best English choice depends on the situation:

• If you are contrasting one group with another, the other volunteers may sound better.
• If some volunteers have already been mentioned and you mean the ones that are left, the rest of the volunteers may sound better.

Hungarian többi naturally covers that idea of the remaining members of a known group.

Here it is a noun: volunteer.

But önkéntes can also function as an adjective, meaning voluntary.

For example:

• önkéntes as a noun: Ő önkéntes. = He/She is a volunteer.
• önkéntes as an adjective: önkéntes munka = voluntary work

In your sentence, a többi önkéntes clearly means the other volunteers, so it is being used as a noun.