Annak ellenére, hogy esik, az önkéntesek összegyűjtik a hulladékot.

As a whole, annak ellenére, hogy means despite the fact that, even though, or in spite of the fact that. It introduces a clause that contrasts with the main action.

So here, it sets up the contrast: Even though it is raining, the volunteers collect the trash.

It is a fixed expression made of three parts:

• annak = of that / despite that in a form required here
• ellenére = despite / in spite of
• hogy = that, introducing a clause

A very literal breakdown is something like despite that, that..., but in natural English you should think of it simply as despite the fact that.

This is a common Hungarian pattern:

• Annak ellenére, hogy fáradt, dolgozik.
  Even though he is tired, he works.

The basic meaning of esik is falls. In weather expressions, Hungarian uses it for rain, so esik by itself usually means it is raining.

So the idea is basically: rain is falling → it is raining

This is one of those everyday expressions you just learn as a set phrase.

Because Hungarian does not use a dummy subject like English it in weather expressions.

English says:

• It is raining

Hungarian just says:

• Esik

So there is no separate word corresponding to English it here.

Hungarian has two forms of the definite article:

• a before a consonant
• az before a vowel

So:

• az önkéntesek because önkéntesek starts with ö, a vowel
• a hulladékot because hulladékot starts with h, treated here like a consonant-starting word

Both mean the.

Because az önkéntesek means the volunteers, not just volunteers in a general sense.

With the article, the sentence sounds like it is talking about a specific group of volunteers, probably already known from the context.

Compare:

• önkéntesek = volunteers / some volunteers
• az önkéntesek = the volunteers

It comes from the verb gyűjt = collect / gather, with the prefix össze-.

The prefix össze- often adds the idea of:

• together
• up
• completely into one place

So összegyűjtik means something like:

• they gather up
• they collect together
• they pick up / collect

In this sentence, collect the trash or gather up the trash is a natural translation.

No. The dictionary form is összegyűjt or gyűjt, not an -ik verb.

The -ik here is not part of the basic verb. It is the ending used here because the verb is:

• 3rd person plural = they
• in the definite conjugation

So összegyűjtik means they collect it / they collect the specific thing.

Because hulladékot is the accusative form, used for the direct object of the verb.

• hulladék = waste / trash
• hulladékot = waste / trash as the thing being acted on

The ending is basically the accusative -t, but here it appears as -ot because Hungarian often inserts a linking vowel for pronunciation.

So:

• a hulladékot = the trash as the object

Because the object is definite: a hulladékot = the trash.

Hungarian verbs often have two kinds of present-tense forms:

• indefinite conjugation when there is no definite object
• definite conjugation when the object is definite

Here the object is definite, so Hungarian uses the definite form:

• összegyűjtik

A useful comparison:

• Hulladékot gyűjtenek. = They collect trash.
  indefinite object → gyűjtenek
• A hulladékot összegyűjtik. = They collect the trash.
  definite object → összegyűjtik

Yes. Hungarian word order is flexible, and it often changes to show emphasis.

The given sentence: Annak ellenére, hogy esik, az önkéntesek összegyűjtik a hulladékot.

This puts the despite/even though part first, so the contrast is emphasized.

You could also say: Az önkéntesek összegyűjtik a hulladékot annak ellenére, hogy esik.

That is also understandable, but the original version is very natural because it foregrounds the bad weather first.

Because annak ellenére, hogy esik is a subordinate clause, and Hungarian normally separates such clauses with a comma.

So the structure is:

• subordinate clause: Annak ellenére, hogy esik
• main clause: az önkéntesek összegyűjtik a hulladékot

The comma is standard punctuation here.

Yes. You could say:

Bár esik, az önkéntesek összegyűjtik a hulladékot.

That means: Although it is raining, the volunteers collect the trash.

The difference is mostly stylistic:

• bár = although
• annak ellenére, hogy = despite the fact that / even though

The longer form sounds a bit more explicit or emphatic.

Also, if you want to use a noun instead of a whole clause, Hungarian often uses:

• az eső ellenére = despite the rain