Mi devas foriri el la kunveno je la oka.

After devas (must / have to), Esperanto uses the infinitive form of the next verb.

• devas foriri = must leave
• not devas foriras

This works like other Esperanto modal-style verbs:

• Mi povas veni. = I can come.
• Ŝi volas dormi. = She wants to sleep.
• Ni devas iri. = We must go.

So in this sentence, foriri stays in the infinitive because it depends on devas.

Iri means to go.

The prefix for- adds the idea of away or off, so:

• iri = to go
• foriri = to go away, to leave

So foriri is more specific than iri. In this sentence, the speaker is not just going somewhere; they are leaving the meeting.

This kind of prefix is very common in Esperanto. Once you know the pieces, many words become easier to understand.

Yes—el literally means out of / from inside.

In Esperanto, el is often used when someone leaves a place, event, group, or enclosed context:

• el la domo = out of the house
• el la urbo = out of the city
• el la kunveno = out of the meeting / from the meeting

English often says leave the meeting, but Esperanto commonly expresses this as foriri el la kunveno.

So even though meeting is not a physical container, Esperanto still treats it naturally as something one can go out of.

Usually, el la kunveno is the better choice here.

• el emphasizes leaving from within something or departing out of it
• de usually means from, but more in the sense of away from, off, or from the possession/surface/proximity of

For a meeting, el la kunveno sounds more natural for leaving the meeting.

Compare:

• Mi venas el la domo. = I am coming out of the house.
• Mi prenas la libron de la tablo. = I take the book from the table.

So el fits better with the idea of departing from participation in the meeting.

Esperanto often tells time with an ordinal adjective, because the full idea is something like at the eighth hour.

So:

• la oka (horo) = the eighth hour
• je la oka = at eight o’clock

The noun horo is often omitted because it is understood.

Examples:

• je la unua = at one o’clock
• je la tria = at three o’clock
• je la deka = at ten o’clock

This is why oka is ordinal rather than cardinal.

Because the expression is short for je la oka horo = at the eighth hour.

Since oka is functioning like an adjective describing an understood noun (horo), Esperanto uses the article:

• la oka (horo)

So je la oka is not just at eight in the abstract; it is literally more like at the eighth hour.

Je is a very flexible preposition in Esperanto. It is often used when no more specific preposition fits well, and one of its most common uses is with clock time.

So:

• je la oka = at eight o’clock
• je la dua kaj duono = at half past two

English uses at for clock times. Esperanto commonly uses je.

You may sometimes see other time expressions without je, especially with dates or parts of the day, but for exact clock time, je is the normal choice.

Esperanto uses la when the speaker has a specific thing in mind and expects the listener to identify it.

Here, la kunveno means the meeting—a particular meeting known from the context.

Compare:

• Mi ĉeestis kunvenon. = I attended a meeting.
  (some meeting, not identified)
• Mi devas foriri el la kunveno. = I have to leave the meeting.
  (a specific meeting)

That matches English pretty closely here.

Esperanto word order is fairly flexible, because the grammar is marked clearly. The most neutral order here is:

• Mi devas foriri el la kunveno je la oka.

But other orders are possible, especially for emphasis:

• Je la oka mi devas foriri el la kunveno.
• El la kunveno mi devas foriri je la oka.

These alternatives may sound more marked or emphasize a different part of the sentence, but they are grammatical.

Still, for learners, the original order is a very natural one.

Sometimes, but the nuance changes.

• eliri = to go out, to exit
• foriri = to go away, to leave

If you say eliri el la kunveno, it can sound a bit more physical, like stepping out.
If you say foriri el la kunveno, it focuses more on departing or leaving altogether.

In many situations, both could make sense, but foriri is a very natural choice for having to leave.

Because no word here is a direct object.

Let’s break it down:

• Mi = subject
• devas foriri = verb idea
• el la kunveno = prepositional phrase
• je la oka = prepositional phrase

The accusative -n is mainly used for direct objects and sometimes for motion toward something. Here, the sentence uses prepositions (el, je) instead, so no accusative is needed.

For comparison:

• Mi vidas la instruiston. = I see the teacher.
  (instruiston gets -n because it is the direct object)

But in your sentence, there is no direct object like that.

By itself, la oka does mean the eighth. Its exact meaning depends on context.

But after je, in a time expression, it is normally understood as the eighth hour, so:

• je la oka = at eight o’clock

If the context were different, la oka could refer to the eighth person, item, chapter, and so on. Here, the time phrase makes the meaning clear.