Klientservo respondis rapide.

In Esperanto, it is very common to build new words by combining roots into a single compound word.

• klient- = client, customer
• servo = service

So klientservo means customer service.

This is a normal and productive pattern in Esperanto. English often uses separate words, but Esperanto frequently joins them into one compound.

The ending -is marks the past tense in Esperanto.

So:

• respondas = answers / is answering
• respondis = answered
• respondos = will answer

Esperanto verb endings are very regular, so once you learn them, they work the same way for all verbs.

The dictionary form is respondi, which means to respond or to answer.

Esperanto verbs appear in different forms depending on tense, but the infinitive always ends in -i:

• respondi = to respond
• respondis = responded
• respondas = responds / is responding

Because rapide is an adverb, and it describes how the action happened.

• rapida = fast, quick (adjective, describes a noun)
• rapide = quickly (adverb, describes a verb)

In this sentence, rapide describes the verb respondis, so the adverb form is needed:

• Klientservo respondis rapide. = Customer service responded quickly.

If you used rapida, it would need to describe a noun, not the action.

It is the subject because it is the thing performing the action respondis.

In this sentence:

• klientservo = the one doing the responding
• respondis = the action
• rapide = how the action was done

Also, there is no -n ending on klientservo, so it is not a direct object here.

Esperanto has no indefinite article like English a/an.

It does have a definite article, la, meaning the, but it is only used when needed.

So:

• klientservo can mean customer service
• la klientservo would mean the customer service

In many sentences, Esperanto leaves out la unless the speaker wants to be specific.

Yes, Esperanto word order is fairly flexible, although subject–verb–adverb is the most straightforward here.

The normal version is:

• Klientservo respondis rapide.

You could also say:

• Rapide respondis klientservo.

That is grammatical, but it sounds more marked or stylistic. For learners, the original order is the safest and most natural choice.

It can often match either respond or answer, depending on context.

So respondis may be translated as:

• responded
• answered

Esperanto words do not always line up perfectly one-to-one with English words, so the best translation depends on the situation.

It is pronounced roughly rah-PEE-deh.

A few helpful pronunciation points:

• r is usually rolled or tapped
• a sounds like ah
• i sounds like ee
• e sounds like eh

Esperanto stress normally falls on the second-to-last syllable, so in rapide, the stress is on pi: ra-PI-de.

Because it is being treated as a singular noun here.

In Esperanto, plural nouns end in -j:

• klientservo = customer service
• klientservoj = customer services

Since the sentence is talking about customer service as one service department or function, the singular form is used.