La dua parto estas pli bona.

La is the definite article, meaning the.

So la dua parto means the second part, not just a second part or second part in a vague sense.

A useful thing to remember: la never changes in Esperanto. It stays la for singular, plural, subject, and object.

Dua means second.

In Esperanto, ordinal numbers are made by adding -a to a number:

• unu = one → unua = first
• du = two → dua = second
• tri = three → tria = third

Because ordinals behave like adjectives, dua has the adjective ending -a.

In Esperanto, nouns normally end in -o.

So:

• parto = part
• libro = book
• domo = house

Here, parto is the noun being talked about: the second part.

Estas is the present-tense form of esti, which means to be.

So estas means is / am / are, depending on context.

One helpful feature of Esperanto: the verb form does not change for person or number.

• mi estas = I am
• vi estas = you are
• li estas = he is
• ili estas = they are

So in this sentence, estas simply means is.

Esperanto usually forms comparisons with pli + adjective.

• bona = good
• pli bona = better
• plej bona = best

So unlike English, Esperanto does not usually make better by changing the adjective itself. It keeps bona and adds pli in front of it.

Bona is an adjective, and adjectives in Esperanto end in -a.

Here it describes parto, saying what the second part is like: it is better.

Even after estas, Esperanto keeps the adjective form:

• La libro estas bona. = The book is good.
• La dua parto estas pli bona. = The second part is better.

So bona stays an adjective, and pli modifies it.

There is no -n because nothing in this sentence is a direct object.

• La dua parto is the subject.
• pli bona is a description linked by estas.

In Esperanto, the accusative -n is mainly used for direct objects and some other special uses, but not for the subject of the sentence and not after esti in a sentence like this.

So:

• La dua parto = subject, no -n
• bona after estas = no -n

Yes.

Since dua is an adjective, it agrees with the noun in number and case.

Here both are singular and not accusative:

• la dua parto

If the noun changed, the adjective would change too:

• la duaj partoj = the second parts
• la duan parton = the second part (as a direct object)

This agreement rule applies to ordinary adjectives and ordinal numbers alike.

Usually, La dua parto estas pli bona is the normal way to say The second part is better.

If you say la pli bona, that means something more like the better one. That can work when you are clearly comparing two things:

• La dua parto estas la pli bona el la du. = The second part is the better one of the two.

So:

• pli bona = better
• la pli bona = the better one

They are related, but not identical.

The normal, easiest word order is:

• La dua parto = subject
• estas = verb
• pli bona = complement

So this sentence follows a very standard pattern.

Esperanto word order is fairly flexible, and other orders are possible for emphasis, but for learners this version is the most natural and clear:

La dua parto estas pli bona.

A rough English-style pronunciation is:

lah DOO-ah PAR-to ESS-tahs plee BOH-nah

A few notes:

• dua has two vowel sounds: du-a
• pli sounds like plee
• bona has clear vowels: bo-na
• stress in Esperanto normally falls on the second-to-last syllable:
  • DU-a
  • PAR-to
  • ES-tas
  • BO-na