La koruso kantas popolan melodion.

Because melodion is the direct object of kantas (sings), and in Esperanto direct objects usually take -n.

The adjective must agree with the noun it describes, so popola also becomes popolan to match melodion.

• melodio = melody
• melodion = a melody / the melody, as the object
• popola melodio = a folk melody
• popolan melodion = a folk melody, as the object

So the -n is not “extra” on the adjective; it is just agreement.

La is the definite article, meaning the.

So:

• La koruso = the choir

There is no article before popolan melodion, so that part is understood as indefinite in English:

• a folk melody

Esperanto has only one article, la, and it does not have a separate word for a/an. If there is no la, the noun is often understood as indefinite, depending on context.

-as marks the present tense in Esperanto.

So:

• kanti = to sing
• kantas = sings / is singing / sing

In Esperanto, the tense ending stays the same for all persons:

• mi kantas = I sing
• vi kantas = you sing
• li kantas = he sings
• la koruso kantas = the choir sings

There is no special -s just for he/she/it, unlike English.

Because the base adjective is popola, from popolo (people, folk, a people).

So:

• popolo = people / folk / nation
• popola = folk, popular, of the people

Then add -n because it agrees with the object noun:

• popola → popolan

It is not based on English spelling or on the word popular directly. Esperanto follows its own regular word-building system.

It can mean choir or chorus, depending on context.

In this sentence, La koruso kantas... most naturally means The choir sings...

A learner might notice the resemblance to English chorus, but here it refers to a group of singers. Context decides the best translation.

Because La koruso is already the subject, so no pronoun is needed.

Esperanto usually states the subject directly:

• La koruso kantas = The choir sings

You would only use a pronoun if you were replacing the noun from earlier context:

• La koruso estas preta. Ĝi kantas popolan melodion.
  = The choir is ready. It is singing a folk melody.

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

The neutral order is:

• La koruso kantas popolan melodion.

But you could also say:

• Popolan melodion kantas la koruso.

That puts more focus on popolan melodion. Because of -n, it is still clear that popolan melodion is the object.

Even so, the standard subject–verb–object order is the most common and usually the best choice for learners.

Esperanto pronunciation is regular, and stress usually falls on the second-to-last syllable of each word.

A rough guide:

• La = lah
• koruso = koh-ROO-so
• kantas = KAN-tahs
• popolan = poh-PO-lahn
• melodion = meh-loh-DEE-on

So the sentence sounds roughly like:

lah koh-ROO-soh KAN-tahs poh-PO-lahn meh-loh-DEE-on

A few useful notes:

• k is always like English k
• o is always a clear o
• a is always ah
• i is like ee

Because it combines two endings:

• -o = noun ending
• -n = accusative/direct object ending

So:

• melodio = melody
• melodion = melody as the direct object

This is very common in Esperanto. The basic noun ending stays, and grammatical endings are added after it.

It is singular.

You can tell because:

• melodio ends in -o, which marks a singular noun
• There is no -j, which would mark the plural

So:

• melodio = melody
• melodioj = melodies
• melodion = a/the melody (object)
• melodiojn = a/the melodies (object, plural)

The adjective would also match:

• popolan melodion = a folk melody
• popolajn melodiojn = folk melodies

Yes.

Esperanto -as simply marks present tense and does not force a difference between:

• sings
• is singing
• sometimes even does sing, depending on context

So La koruso kantas popolan melodion could mean either:

• The choir sings a folk melody
• The choir is singing a folk melody

The surrounding context tells you which is more natural.

Because in Esperanto, ordinary nouns are not capitalized the way they are in German.

Only things like:

• the first word of a sentence
• proper names
• some special titles or abbreviations

get capital letters.

So in this sentence:

• La is capitalized because it starts the sentence
• koruso, kantas, popolan, and melodion are common words, so they stay lowercase

The dictionary forms are:

• la = the
• koruso = choir / chorus
• kanti = to sing
• popola = folk, popular, of the people
• melodio = melody

In the sentence:

• kantas comes from kanti
• popolan comes from popola
• melodion comes from melodio

This is a very normal pattern in Esperanto: dictionary forms are easy to recognize because the endings are regular.