La alvenonta gasto jam sendis mesaĝon.

Alvenonta is the future active participle of alveni (to arrive).

It breaks down like this:

• alven- = the verb root arrive
• -ont- = future active participle marker
• -a = adjective ending

So alvenonta literally means going to arrive, about to arrive, or forthcoming.

In this sentence, la alvenonta gasto means the guest who will arrive or the arriving guest.

Because it is functioning as an adjective and describing gasto.

In Esperanto, adjectives always end in -a:

• bona gasto = a good guest
• nova domo = a new house
• alvenonta gasto = a guest who is going to arrive

Since alvenonta describes the noun gasto, it must have the adjective ending -a.

La is the definite article, meaning the.

So la alvenonta gasto means not just an arriving guest, but the arriving guest — a specific guest that the speaker and listener can identify from context.

Esperanto has only one article, la, and it does not change for gender, number, or case.

Sendis is the past tense form of sendi (to send).

Esperanto verbs are very regular:

• sendas = sends / is sending
• sendis = sent
• sendos = will send

So jam sendis mesaĝon means has already sent a message or literally already sent a message.

Esperanto often uses the simple past where English might use the present perfect.

Esperanto does not have a separate tense that exactly matches the English present perfect.

Instead, it usually uses the ordinary past tense when English would say has sent:

• Li venis = He came / He has come
• Ŝi skribis = She wrote / She has written
• La gasto jam sendis mesaĝon = The guest has already sent a message

The word jam helps show that the action was completed before now, which often makes English use already has/have.

Jam means already.

It shows that the action happened earlier than expected or earlier than some reference point.

So:

• La gasto sendis mesaĝon = The guest sent a message
• La gasto jam sendis mesaĝon = The guest already sent / has already sent a message

In this sentence, jam makes it clear that the message has been sent before the guest has arrived.

The -n marks the direct object.

The direct object is the thing that receives the action of the verb. Here, what was sent? A message.

• La gasto sendis mesaĝon = The guest sent a message
• mesaĝon is what was sent, so it gets -n

This is called the accusative ending.

Compare:

• La gasto venis = The guest came
• La gasto sendis mesaĝon = The guest sent a message

In the second sentence, mesaĝo becomes mesaĝon because it is the object.

Because gasto is the subject, not the object.

The subject is the one doing the action. In this sentence, the guest is doing the sending.

• La alvenonta gasto = the one who sent
• mesaĝon = the thing that was sent

Only the direct object gets -n here.

Yes. Esperanto word order is fairly flexible because the -n ending helps show what is the object.

The most neutral order is:

• La alvenonta gasto jam sendis mesaĝon.

But you could also say, for example:

• Jam la alvenonta gasto sendis mesaĝon.
• Mesaĝon jam sendis la alvenonta gasto.

These alternatives may sound more marked or emphasize different parts of the sentence, but the basic meaning remains understandable because mesaĝon is clearly marked as the object.

For learners, the standard subject–verb–object order is the safest and most natural choice.

They mean almost the same thing:

• la alvenonta gasto = the guest who will arrive / the arriving guest
• la gasto, kiu alvenos = the guest who will arrive

The first version uses a participle and is more compact.
The second version uses a full relative clause.

Esperanto often likes participles because they are concise and elegant, but both forms are correct.

Both are possible in some contexts, but they are not exactly identical.

• veni = to come
• alveni = to arrive

So:

• venonta gasto = the guest who is going to come
• alvenonta gasto = the guest who is going to arrive

Alveni focuses more on reaching the destination, so it often feels especially natural when you mean someone expected to show up at a place.

Not necessarily.

Alvenonta means going to arrive or expected to arrive. It points to a future arrival, but it does not by itself say exactly when.

Depending on context, it could mean:

• arriving soon
• arriving later today
• arriving at some known future time

If you wanted to emphasize that the guest is arriving right now, you would more likely use something like alvenanta instead.

This is an important distinction:

• alvenanta = arriving / in the process of arriving
• alvenonta = going to arrive / yet to arrive

So:

• la alvenanta gasto = the guest who is arriving
• la alvenonta gasto = the guest who will arrive

In your sentence, the guest has not necessarily arrived yet; the sentence only says that this future guest has already sent a message.

Because Esperanto does not require an article where English might say a or the.

Esperanto has la for the, but it has no separate word for a/an.

So:

• mesaĝo can mean a message
• la mesaĝo means the message

In the sentence, mesaĝon most naturally means a message unless the context makes it definite.

Yes — and that is probably the most natural interpretation.

Because the person is described as alvenonta (going to arrive), the sentence strongly suggests that the arrival is still in the future relative to the speaker’s reference point.

So the idea is something like:

The guest who is due to arrive has already sent a message.

That contrast between future arrival and already sent is exactly what makes jam useful here.