Honesta respondo estas pli utila ol bela mensogo.

In Esperanto, -a is the adjective ending.

So in this sentence:

• honesta = honest
• utila = useful
• bela = beautiful / nice

Adjectives always end in -a, no matter what they mean. They also agree with the noun they describe in number and case, but here everything is singular and not accusative, so the simple -a form is used.

Because -o is the noun ending in Esperanto.

• respondo = answer / response
• mensogo = lie

This makes Esperanto very regular: if you see -o, you can immediately recognize a noun.

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

So:

• estas = is / are / am

Esperanto does not change the verb for different subjects the way English does. The same form works with all persons:

• mi estas
• vi estas
• li estas
• ili estas

Here, Honesta respondo estas... means An honest answer is...

Pli ... ol is the standard way to make comparisons in Esperanto.

• pli = more
• ol = than

So:

• pli utila ol = more useful than

This works much like English:

• pli granda ol = bigger than
• pli rapida ol = faster than
• pli bona ol = better than

In the sentence, Honesta respondo estas pli utila ol bela mensogo means that one thing is more useful than another.

Because the sentence needs an adjective after estas.

In Esperanto, after esti (to be), you often use an adjective to describe the subject:

• La domo estas granda. = The house is big.
• La libro estas interesa. = The book is interesting.

So here:

• Honesta respondo = the subject
• estas pli utila = is more useful

Utila is simply the adjective useful.

Because there is no direct object here.

This is a sentence built around estas (is), which links the subject to a description. The nouns are not being acted upon as direct objects.

Structure:

• Honesta respondo = subject
• estas pli utila = linking verb + description
• ol bela mensogo = comparison phrase

Since neither noun is a direct object, no accusative -n is needed.

Esperanto usually does not use an indefinite article.

English says:

• an honest answer
• a beautiful lie

Esperanto normally just says:

• honesta respondo
• bela mensogo

There is a definite article, la, meaning the, but there is no separate word for a/an.

Yes, depending on context.

• La honesta respondo estas pli utila ol la bela mensogo.

That would mean something more like The honest answer is more useful than the beautiful lie, referring to specific things already known in context.

Without la, the sentence sounds more general, like a general truth or principle.

Because that is the normal, most common position in Esperanto.

• honesta respondo
• bela mensogo

Adjectives can sometimes come after nouns in Esperanto, but before the noun is the usual and most natural order, especially for learners.

So this sentence uses the standard pattern:

• adjective + noun

Not always exactly, though they are very close.

Respondo can mean:

• answer
• response
• reply

In this sentence, answer is probably the most natural English idea, but Esperanto respondo is a broad, everyday word.

Mensogo means a lie, so it usually implies intentional falsehood.

That is different from simply being mistaken. If someone says something untrue by accident, that is not necessarily a mensogo.

So bela mensogo means a lie that sounds pleasing, attractive, comforting, or pretty in some sense.

Yes, Esperanto word order is fairly flexible, but the original order is the clearest and most neutral.

For example, this would still be understandable:

• Pli utila estas honesta respondo ol bela mensogo.

But the standard learner-friendly order is:

• Honesta respondo estas pli utila ol bela mensogo.

That order makes the structure easy to see:

1. subject
2. verb
3. comparison

A simple pronunciation guide is:

hoh-NES-tah reh-SPON-doh ES-tahs plee oo-TEE-lah ol BEH-lah men-SOH-goh

A few useful points:

• h is pronounced
• e is like e in bet
• o is like o in a pure for-type vowel, not a diphthong
• j would sound like y, though there is no j in this sentence
• stress is always on the second-to-last syllable:
  • hoNESta
  • reSPONdo
  • esTAS
  • uTIla
  • menSOgo

That regular stress pattern is one of Esperanto’s easiest features to learn.