Ili enscenigos la teatraĵon morgaŭ.

Because -os is the Esperanto ending for the future tense.

• enscenigas = stage / are staging
• enscenigis = staged
• enscenigos = will stage

So Ili enscenigos la teatraĵon morgaŭ means the action will happen in the future.

Enscenigi means to put on stage, to stage, or to produce for performance.

It is built from parts:

• en- = in, into
• scen- = scene / stage-related idea
• -ig- = make, cause
• -i = infinitive ending

So the basic idea is to cause something to be on stage.

The suffix -ig- usually means to make something become or to cause something to do something.

In many Esperanto words, it adds a causative idea:

• sidi = to sit
• sidigi = to seat someone, make someone sit

Here:

• ensceni would suggest something like to be on stage / place on stage
• enscenigi gives the clearer sense to stage something, to bring it onto the stage as a production

So -ig- is helping create the idea of causing a play to be presented on stage.

The -n marks the direct object.

In this sentence, la teatraĵon is the thing being staged. They are staging the play.

• Ili enscenigos la teatraĵo would be incorrect
• Ili enscenigos la teatraĵon is correct

Esperanto uses -n to show which noun receives the action, so word order can be more flexible.

Teatro usually means theater as a place or the art form.

Teatraĵo means a theatrical piece, a play, or a drama/performance work.

That -aĵ- suffix often means a concrete thing characterized by the root.

So:

• teatro = theater
• teatra = theatrical
• teatraĵo = a theatrical work, a play

In this sentence, they are staging the play, not the theater building.

La is the definite article, meaning the.

So la teatraĵon means the play, not just a play.

Esperanto has only one article, la, and it does not change for gender, number, or case. Even though teatraĵon has -n, the article stays la.

Yes, to some extent.

Because teatraĵon has the object marker -n, Esperanto does not rely as heavily on word order as English does. These all keep basically the same meaning:

• Ili enscenigos la teatraĵon morgaŭ.
• Morgaŭ ili enscenigos la teatraĵon.
• La teatraĵon ili enscenigos morgaŭ.

However, the most neutral and natural order is usually:

• subject + verb + object + time

So the original sentence sounds very normal.

No. Morgaŭ can move around fairly freely.

For example:

• Ili enscenigos la teatraĵon morgaŭ.
• Morgaŭ ili enscenigos la teatraĵon.
• Ili morgaŭ enscenigos la teatraĵon.

All are grammatical. The choice depends on emphasis and style.

Putting morgaŭ first often emphasizes the time: Tomorrow, they will stage the play.

No. Ili means they.

It is always plural. It does not mean he, she, or it.

Some useful pronouns for comparison:

• li = he
• ŝi = she
• ĝi = it
• ili = they

So Ili enscenigos... clearly means They will stage...

Ĵ is pronounced like the s in measure or the g in genre.

A rough pronunciation of teatraĵon is:

teh-ah-TRAH-zhon

A few pieces:

• te-a-tra = each vowel is pronounced clearly
• ĵo = like zho
• -n = pronounced normally

Also remember that Esperanto stress normally falls on the second-to-last syllable, so:

te-a-TRA-ĵon

It can be used for both.

The Esperanto future ending -os simply means the action is future. It does not by itself tell you whether the action is:

• happening soon
• happening much later
• merely predicted
• already planned

Context tells you that. In this sentence, morgaŭ makes it clear the event is tomorrow, and the sentence could easily describe a planned production.

You would say:

Ili enscenigos ĝin morgaŭ.

Here:

• ĝin = it as a direct object
• it also takes -n, because it is the object of the verb

So:

• la teatraĵon = the play
• ĝin = it

Both fill the same grammatical role in the sentence.