Ni lernas unu de la alia.

Literally, it means one from the other.

In this sentence, Esperanto uses a reciprocal pattern that often looks more literal than the English each other. So:

• Ni = we
• lernas = learn
• unu de la alia = one from the other / from each other

So the whole sentence is literally something like We learn, one from the other, but naturally it means We learn from each other.

Because unu de la alia is part of a fixed reciprocal expression.

Esperanto often expresses each other with forms built from unu (one) and alia (the other). The idea is not that there is only one person involved, but that the people in the group relate to one another pairwise:

• unu ... la alia = one ... the other
• in plural situations, this gives the sense of each other

So even with ni, the singular unu is normal here.

The la is part of the standard reciprocal construction.

Esperanto commonly says:

• unu la alian = each other
• unu de la alia = from each other
• unu al la alia = to each other
• unu kun la alia = with each other

So la alia is not just random here; it belongs to the established pattern. Native English speakers often want to drop la, but in this expression it normally stays.

Because lerni de means to learn from someone or something.

In Esperanto, lerni can take different kinds of complements:

• lerni ion = learn something
• lerni de iu = learn from someone

So in Ni lernas unu de la alia, the preposition de is there because the meaning is learn from.

Because unu la alian means each other as a direct object, but here the idea is from each other, which needs the preposition de.

Compare:

• Ni amas unu la alian. = We love each other.
  
  • Here each other is the direct object of amas.
• Ni lernas unu de la alia. = We learn from each other.
  
  • Here the relationship is introduced by de.

So the form changes depending on the preposition or grammatical role involved.

Because it is governed by the preposition de.

In Esperanto, prepositions normally take the basic form, not the accusative -n. So:

• de la alia = from the other
• al la alia = to the other
• kun la alia = with the other

You would see -n in a form like unu la alian, because there alian is a direct object. But after de, you use alia, not alian.

Yes. It is a very common pattern for expressing reciprocal ideas after different prepositions.

Some useful examples:

• unu la alian = each other
• unu al la alia = to each other
• unu de la alia = from each other
• unu kun la alia = with each other
• unu pri la alia = about each other

So this sentence is following a broader and very useful Esperanto structure.

Not really. A word-for-word translation would sound awkward in English: We learn one from the other.

That literal version helps show the Esperanto structure, but natural English is:

• We learn from each other.

This is one of those cases where Esperanto and English organize the same idea differently.

The standard and clearest form is Ni lernas unu de la alia.

Esperanto does allow some flexibility in word order, but with set reciprocal expressions like this, learners should stick to the usual pattern. That makes your Esperanto sound natural and easy to understand.

So for practical purposes, treat unu de la alia as a unit.

It can be used with other plural subjects too.

For example:

• Ili lernas unu de la alia. = They learn from each other.
• La studentoj lernas unu de la alia. = The students learn from each other.

The reciprocal phrase does not depend specifically on ni; it works whenever the subject involves more than one participant.