Kiam la ĉielo ne plu estas hela, mia patrino ŝaltas la lampon en la salono.

Kiam means when and introduces a subordinate time clause.

So in Kiam la ĉielo ne plu estas hela, everything up to the comma is the when-clause, and the main clause comes after it: mia patrino ŝaltas la lampon en la salono.

Esperanto does not change the normal word order after kiam. It stays straightforward:

• la ĉielo = subject
• estas = verb
• hela = predicate adjective

The comma separates the subordinate clause from the main clause.

• Kiam la ĉielo ne plu estas hela = subordinate clause
• mia patrino ŝaltas la lampon en la salono = main clause

Using a comma like this is normal and helpful in Esperanto, especially when the sentence begins with a subordinate clause.

Ne plu means no longer or not anymore.

• plu has the idea of further / any more
• with ne, it becomes not any more

So:

• ne plu estas hela = is no longer bright

This is a very common expression in Esperanto.

La is the definite article, meaning the.

In Esperanto, you often use la when talking about something specific or understood from context. La ĉielo means the sky, which is naturally a specific thing.

Unlike English, Esperanto has only one definite article:

• la for all nouns
• no separate forms for gender, number, or case

Because hela is an adjective, and it describes la ĉielo.

• -a = adjective
• -e = adverb

Here the sentence says the sky is bright, so you need an adjective:

• hela = bright

If you said hele, that would mean brightly, which would be an adverb and would not fit here.

It already matches the noun correctly.

In Esperanto:

• adjectives end in -a
• they agree with nouns in number and case

Here:

• ĉielo is singular
• it is not accusative

So the adjective stays singular and non-accusative too:

• hela

If the noun were plural, you would get helaj. If it were accusative, you would get helan.

In Esperanto, possessive words like mia, via, lia, ŝia, and so on usually make the noun definite by themselves.

So you normally say:

• mia patrino = my mother

Not:

• la mia patrino

That second version is generally not used in normal Esperanto for this meaning.

Patrino is built from parts:

• patr- = parent/father-related root
• -in- = female suffix
• -o = noun ending

So:

• patro = father
• patrino = mother

This is a very useful Esperanto pattern:

• frato = brother
• fratino = sister
• kato = male or unspecified cat in some usage, but often just cat
• katino = female cat

Ŝaltas is present tense because the sentence describes what happens in a general or habitual situation.

It means something like:

• whenever the sky is no longer bright, my mother turns on the lamp

Esperanto often uses the present tense for repeated or habitual actions, just like English can:

• When it gets dark, she turns on the lamp

So ŝaltas does not have to mean only right now. It can also express a regular action.

Because it is the direct object of ŝaltas.

Ask:

• My mother turns on what?

Answer:

• la lampon

In Esperanto, direct objects take the accusative ending -n:

• lampo = lamp
• lampon = lamp as the direct object

This is one of the most important grammar rules in Esperanto.

Because here en shows location, not movement.

• en la salono = in the living room / in the lounge
• this tells you where the lamp is turned on

In Esperanto, after a preposition like en, you usually do not use -n unless you want to show direction or movement toward somewhere.

Compare:

• en la salono = in the living room
• en la salonon = into the living room

Here there is no movement into the room, just location, so salono stays without -n.

Yes. Esperanto has fairly flexible word order because endings show grammatical roles clearly.

For example, you could also say:

• Mia patrino ŝaltas la lampon en la salono, kiam la ĉielo ne plu estas hela.

That is still grammatical.

But the original order is very natural because it begins with the time setting:

• When the sky is no longer bright, ...

The main special letters here are:

• ĉ as in church
• ŝ as in shoe

So roughly:

• ĉielo ≈ chee-EH-lo
• ŝaltas ≈ SHAL-tas

A few extra pronunciation points:

• Esperanto stress usually falls on the second-to-last syllable
• each letter has a regular pronunciation

So:

• ĉielo → stress on e
• patrino → stress on tri
• salono → stress on lo

Esperanto often expresses ideas in a simple, transparent way.

Here the sentence says literally that the sky is no longer bright:

• ne plu estas hela

That is perfectly natural Esperanto.

A learner should notice that Esperanto does not always choose the same wording English would prefer. Instead of using one verb like darkens, it may use a clear phrase built from familiar parts.

In this sentence, plu works like a small adverb-like word meaning further / any more.

It is very often used with ne:

• ne plu = no longer

You will also see it in expressions like:

• Mi ne volas plu atendi. = I do not want to wait any longer.
• Ĉu vi volas plu? = Do you want more / further?

So it is a very common and useful word to learn early.