Mi tranĉas cepon por la salato.

Because cepon is the direct object of the verb tranĉas.

In Esperanto, the direct object usually takes the accusative ending -n:

• cepo = onion
• cepon = onion, as the thing being cut

So in Mi tranĉas cepon, the onion is what the speaker is cutting, so it gets -n.

By contrast, la salato does not get -n here because it comes after the preposition por.

La means the. Esperanto has a definite article, but it does not have an indefinite article like English a/an.

So:

• cepon = an onion or just onion, depending on context
• la salato = the salad

This sentence suggests that the salad is a specific one already understood in context, while the onion is not being identified as a specific onion.

If you wanted to say the onion, you could say la cepon.

In Esperanto, the present tense ending -as covers all of those present-time meanings, depending on context.

So Mi tranĉas can mean:

• I cut
• I am cutting
• sometimes even I do cut

Usually English chooses between simple present and progressive, but Esperanto often just uses -as and lets context do the work.

Because ordinary Esperanto usually does not need a special progressive form.

English often distinguishes:

• I cut
• I am cutting

Esperanto normally just uses the simple present:

• Mi tranĉas

There are ways to be more explicit, but they are less common and usually unnecessary for basic statements.

Por means for in the sense of for the benefit of, for the purpose of, or intended for.

So por la salato means:

• for the salad
• for use in the salad

It tells you the purpose of cutting the onion.

A common learner confusion is between por and pro:

• por = for, intended for, in order to
• pro = because of, due to

So here por is correct because the onion is being cut in order to use it in the salad.

Because it is part of a prepositional phrase: por la salato.

In Esperanto, nouns after prepositions usually do not take the accusative ending just because they follow a preposition.

So:

• cepon gets -n because it is the direct object
• la salato does not get -n because it is the object of por

Yes. That would mean I am cutting the onion for the salad.

The difference is:

• Mi tranĉas cepon por la salato = I’m cutting an onion / onion for the salad
• Mi tranĉas la cepon por la salato = I’m cutting the onion for the salad

So adding la makes the onion definite.

Yes. That would mean I am cutting onions for the salad.

Here:

• cepon = one onion
• cepojn = onions

The plural ending is -j, and the accusative ending -n is added after that:

• cepo → onion
• cepoj → onions
• cepojn → onions, as direct object

Not completely. Esperanto word order is fairly flexible, because endings show the grammatical roles.

The most neutral order is:

• Mi tranĉas cepon por la salato.

But you could also say:

• Por la salato mi tranĉas cepon.

That puts more emphasis on for the salad.

Still, the standard subject-verb-object order is usually easiest for learners.

The letter ĉ is pronounced like ch in church.

So tranĉas sounds roughly like:

• TRAN-chas

A few helpful points:

• c in Esperanto is always like ts
• ĉ is always like English ch
• each letter has a consistent sound

So:

• cepo starts with ts, not with English s or k
• tranĉas contains the ch sound

Yes. Cepo is the normal Esperanto word for onion.

In ordinary usage, it can refer to the onion as food, just like English onion does.

So in this sentence, cepon naturally means an onion being cut for cooking or preparing food.

Yes, depending on context.

Because Esperanto has no indefinite article, cepon can sometimes feel a bit broader than English an onion. In many contexts it simply means that onion is what you are cutting.

If you want to be very specific, context usually handles it:

• Mi tranĉas cepon = I’m cutting an onion
• Mi tranĉas cepojn = I’m cutting onions

So the singular form usually suggests one onion, but the exact nuance can depend on the situation.