Ne nur volontuloj, sed ankaŭ artistoj partoprenas.

It is the standard Esperanto pattern for not only ... but also ....

So in this sentence:

• ne nur volontuloj = not only volunteers
• sed ankaŭ artistoj = but also artists

This structure is very common in Esperanto and works much like the English one.

The ending -oj marks a noun as plural in Esperanto.

• volontulo = a volunteer

• volontuloj = volunteers

• artisto = an artist
• artistoj = artists

So both words are plural because the sentence is talking about more than one volunteer and more than one artist.

Because they are the subject, not the direct object.

In Esperanto, -n is usually added for the direct object. But here, volontuloj and artistoj are the ones doing the action of partoprenas.

So:

• volontuloj partoprenas = volunteers participate
• artistoj partoprenas = artists participate

No -n is needed.

Because Esperanto verbs do not change according to person or number.

The ending -as always means present tense, no matter whether the subject is:

• mi = I
• li = he
• ili = they
• volontuloj kaj artistoj = volunteers and artists

So all of these use the same present-tense ending:

• mi partoprenas
• li partoprenas
• ili partoprenas

That is one of the simplest features of Esperanto grammar.

Partoprenas is the present-tense form of partopreni, which means to participate or to take part.

Breakdown:

• partopreni = to participate
• partoprenas = participates / participate / is participating

The -as ending shows present tense.

So artistoj partoprenas means artists participate or artists are taking part.

Because Esperanto does not use la as often as English uses the.

In this sentence, the speaker is talking about the groups volunteers and artists in a general or category sense, not necessarily as specifically identified groups already known to the listener.

So:

• volontuloj = volunteers
• artistoj = artists

If the context were about particular known people, you might see la volontuloj or la artistoj instead.

The comma helps show the break between the two parts of the pattern:

• ne nur ...
• sed ankaŭ ...

It marks a natural pause and makes the sentence easier to read.

Especially before sed (but), a comma is very common in Esperanto writing.

Yes. Esperanto has fairly flexible word order because the endings help show how words function.

This version is natural and clear:

• Ne nur volontuloj, sed ankaŭ artistoj partoprenas.

But other orders are possible for emphasis, such as:

• Partoprenas ne nur volontuloj, sed ankaŭ artistoj.

That said, the original order is probably the most straightforward for a learner.

In this structure, sed ankaŭ is the normal pairing.

• sed = but
• ankaŭ = also

Together they correspond to English but also.

So ne nur ... sed ankaŭ ... is a set expression. A learner should treat it as a common fixed pattern rather than trying to build it word by word each time.

Yes, but the emphasis changes.

For example, you could say:

• Volontuloj kaj artistoj partoprenas.
  = Volunteers and artists participate.

This gives the basic information, but it does not emphasize the contrast or addition in the same way.

The original sentence highlights that artists are included in addition to volunteers:

• Not only volunteers, but also artists participate.

So the ne nur ... sed ankaŭ ... pattern is used when that extra emphasis matters.