Pendigu la afiŝon sur la muron de la biblioteko.

In Esperanto, -u is the verb ending for the imperative/jussive form: commands, requests, or suggestions.

So Pendigu means something like:

• Hang up!
• Please hang up
• Let [someone] hang up

In this sentence, it is a direct command to one or more people.

This is a very good question, because the two forms are related but not identical.

• pendi = to hang in the sense of be hanging
• pendigi = to cause to hang, to hang up, to suspend

So:

• La afiŝo pendas. = The poster is hanging.
• Pendigu la afiŝon. = Hang up the poster.

English often uses hang for both ideas, but Esperanto often distinguishes them more clearly.

The -n marks the direct object.

Here, la afiŝon is the thing being hung up, so it receives the action of the verb:

• Pendigu kion? = Hang up what?
• la afiŝon = the poster

That is why afiŝo becomes afiŝon.

Because Esperanto often uses -n after a preposition to show movement toward a place.

Compare:

• sur la muro = on the wall (location, no movement)
• sur la muron = onto the wall / to the wall (movement toward that position)

In this sentence, the poster is being moved from somewhere else and placed onto the wall, so muron is correct.

Yes. Grammatically, it means onto the wall or to the wall, because of the -n of direction.

However, in natural English, we often say Hang the poster on the wall, even though movement is implied. So the Esperanto is a bit more explicit here than the usual English translation.

de usually means of, from, or shows a relationship like possession or association.

Here:

• la muro de la biblioteko = the wall of the library / the library’s wall

So de la biblioteko tells you which wall: the wall belonging to or associated with the library.

Esperanto uses la as the definite article, meaning the.

In this sentence:

• la afiŝon = the poster
• la muron = the wall
• la biblioteko becomes la biblioteko inside de la biblioteko = of the library

Esperanto does not usually contract articles, and each noun phrase can have its own la, just as English can say the poster on the wall of the library.

Yes, Esperanto word order is fairly flexible, but some orders sound more neutral than others.

The given sentence:

• Pendigu la afiŝon sur la muron de la biblioteko.

is a normal, clear order.

You might also see variations for emphasis, but the basic meaning stays clear because:

• -n marks the direct object
• prepositions show relationships

Still, for learners, the given order is the safest and most natural.

afiŝo means a poster, placard, or notice posted up.

It usually refers to something meant to be displayed publicly, such as:

• an event poster
• a notice on a wall
• an advertisement poster

So in this sentence, it is something you can physically hang or stick up for people to see.

Not if you want the same meaning.

• sur la muron de la biblioteko = onto the wall of the library
• sur la muron en la biblioteko = onto the wall in the library

These are similar, but not identical.

de la biblioteko identifies the wall as belonging to the library.
en la biblioteko identifies the location as being inside the library.

Sometimes both could make sense in real life, but they are grammatically different ideas.

Yes. In Esperanto, prepositions are normally followed by the basic form, but when a prepositional phrase shows direction toward a place, the noun often takes -n.

So:

• sur la tablo = on the table (location)
• sur la tablon = onto the table (direction)

The same pattern appears here:

• sur la muron = onto the wall

This is one of the most important uses of the accusative in Esperanto besides marking direct objects.