Kiam la aŭto subite bremsis, la policistino tuj demandis, kial la ŝoforo ne portis sekurzonon.

Kiam means when. Here it introduces a subordinate clause:

Kiam la aŭto subite bremsis = When the car suddenly braked

This sets the time background for the main action in the rest of the sentence.

A useful pattern is:

• Kiam + clause, main clause
• When + clause, main clause

So the sentence is built like:

• Kiam la aŭto subite bremsis, ...
• When the car suddenly braked, ...

In Esperanto, a comma is normally used to separate a subordinate clause from the main clause.

So:

• Kiam la aŭto subite bremsis, = subordinate clause
• la policistino tuj demandis... = main clause

You will often see this with words like kiam (when), ĉar (because), se (if), kvankam (although), and so on.

Bremsis comes from bremsi = to brake.

The ending -is is the Esperanto past tense. So:

• bremsi = to brake
• bremsas = brakes / is braking
• bremsis = braked
• bremsos = will brake

In this sentence, the braking happened in the past, so bremsis is used.

Subite means suddenly. It is an adverb, and adverbs in Esperanto usually end in -e.

So:

• subita = sudden
• subite = suddenly

It describes how the car braked:

• la aŭto subite bremsis = the car suddenly braked

La is the definite article, meaning the.

So:

• policistino = a policewoman / police officer
• la policistino = the policewoman

Esperanto uses la when the speaker has a specific person or thing in mind. In this sentence, it is a particular police officer in the situation, so la is natural.

Policisto means police officer (traditionally also policeman in some contexts).
The suffix -in- marks female sex, so:

• policisto = police officer
• policistino = female police officer / policewoman

This is a very common Esperanto pattern:

• patro = father
• patrino = mother
• instruisto = teacher
• instruistino = female teacher

Tuj means immediately, right away, or at once.

Here:

• la policistino tuj demandis = the policewoman immediately asked

Its position is fairly natural, but Esperanto word order is flexible. You could also see similar adverbs in slightly different places depending on style or emphasis.

Demandi means to ask.

So:

• demandis = asked

In this sentence, the policewoman asked a question, and that question is given in indirect form after it:

• la policistino tuj demandis, kial...
• the policewoman immediately asked why...

Because kial la ŝoforo ne portis sekurzonon is another subordinate clause, specifically an indirect question.

So the structure is:

• la policistino tuj demandis, kial la ŝoforo ne portis sekurzonon
• the policewoman immediately asked why the driver was not wearing a seat belt

Esperanto often separates this kind of clause with a comma.

Kial means why.
Kiam means when.

So in this sentence:

• Kiam la aŭto subite bremsis = When the car suddenly braked
• kial la ŝoforo ne portis sekurzonon = why the driver wasn’t wearing a seat belt

They look similar because both are part of the ki- set of question/correlative words:

• kiu = who / which
• kio = what
• kie = where
• kiam = when
• kial = why
• kiel = how

Because kial already introduces the clause by itself.

Esperanto does not say:

• *demandis, ke kial...

Instead, you simply use the question word directly:

• demandis, kial... = asked why...
• demandis, ĉu... = asked whether...
• demandis, kie... = asked where...

This works like English indirect questions.

Ŝoforo means driver.

The letter ŝ is pronounced like English sh, so ŝoforo sounds roughly like sho-FO-ro.

In this sentence:

• la ŝoforo = the driver

For the same reason as la aŭto and la policistino: it refers to a specific, identifiable person in the situation.

• la ŝoforo = the driver
• ŝoforo = a driver

Since this is the driver of that car in that event, Esperanto naturally uses la.

Yes. Esperanto often uses the simple past where English might use a progressive form.

So:

• portis can mean wore or was wearing, depending on context.

In this sentence:

• la ŝoforo ne portis sekurzonon

is naturally understood as:

• the driver was not wearing a seat belt

Esperanto usually does not need a special continuous form like English was wearing unless you really want to emphasize ongoing action in some other way.

Yes, porti can mean both to carry and to wear.

That is normal in Esperanto. The exact meaning comes from context.

Examples:

• porti sakon = to carry a bag
• porti ĉapelon = to wear a hat
• porti sekurzonon = to wear a seat belt

So here, because the object is sekurzono, the meaning is clearly wear.

The ending -n marks the direct object in Esperanto.

Here, sekurzonon is the thing being worn:

• portis sekurzonon = wore a seat belt

Without the -n, it would be grammatically incomplete in standard Esperanto.

Compare:

• La ŝoforo portis sekurzonon. = The driver wore a seat belt.
• La ŝoforo portis ĉapelon. = The driver wore a hat.

Both sekurzonon and ĉapelon are direct objects, so they take -n.

It is a compound word:

• sekur- = safety / secure
• zono = belt

So:

• sekurzono = seat belt / safety belt

Compounds are very common in Esperanto, and they are often easy to understand once you know the parts.

Because the whole situation is being described as a past event.

• bremsis = the car braked
• demandis = the policewoman asked
• portis = the driver was wearing / wore

Esperanto keeps tense usage fairly straightforward. If something happened in the past, -is is usually enough.

English sometimes uses different past forms like braked, asked, was wearing, but Esperanto often just uses the plain past tense throughout.

Yes, grammatically it could. But in this context, was not wearing is the more natural English translation.

That is because the police officer is asking about the driver’s state at that moment, not about a general habit.

So:

• ne portis sekurzonon literally matches did not wear a seat belt
• but natural English here is was not wearing a seat belt

Not completely. Esperanto word order is more flexible than English because endings show the grammatical roles.

For example, subite could move:

• la aŭto subite bremsis
• la aŭto bremsis subite

Both are understandable, though the first sounds more natural here.

Likewise, adverbs like tuj can move somewhat too. But the original order is very normal and clear.

Aŭ is a diphthong, pronounced roughly like ow in English cow.

So:

• aŭto sounds roughly like OW-to

Other useful pronunciation points in this sentence:

• ŝ = sh
• ŭ is a short glide sound, not a full vowel
• stress in Esperanto normally falls on the second-to-last syllable:
  • AŬ-to
  • po-li-ci-STI-no
  • de-man-DIS
  • se-kur-ZO-non

Because all three are specific in the situation being described:

• la aŭto = the car involved
• la policistino = the policewoman there
• la ŝoforo = the driver of that car

Esperanto has only one article, la, and no separate word for English a/an. If something is indefinite, Esperanto usually just leaves out the article:

• aŭto = a car
• policistino = a policewoman
• ŝoforo = a driver

But here the nouns are definite, so la is used.