La sistemo de hejtado ne funkcias.

This is a very common Esperanto pattern: noun + de + noun.

So sistemo de hejtado is literally system of heating, which is how Esperanto expresses the idea of a heating system in a very transparent way.

Here, de shows a relationship between the two nouns. It is not a quantity word. That is why it is de, not da.

• de = of, from, belonging to, related to
• da = used after words of quantity, like multe da akvo

So sistemo de hejtado is correct, but sistemo da hejtado would be wrong.

Because hejti is a verb in the infinitive, meaning to heat, while hejtado is a noun, meaning heating.

After de in this sentence, Esperanto uses a noun phrase, not an infinitive verb. So:

• hejti = to heat
• hejtado = heating

That makes de hejtado the natural form here.

The suffix -ad- usually emphasizes an action as a process, ongoing activity, or repeated action.

So:

• hejti = to heat
• hejtado = heating, the process/activity of heating

In this sentence, that makes sense because a heating system is a system used for the process of heating, not just a single act of heating once.

Yes. That is also good Esperanto.

There are several natural ways to express this idea:

• La sistemo de hejtado ne funkcias.
• La hejta sistemo ne funkcias.
• La hejtsistemo ne funkcias.

They are all understandable and correct.

Very roughly:

• sistemo de hejtado sounds a bit more analytical and explicit
• hejta sistemo uses an adjective
• hejtsistemo is a compound noun

For a learner, sistemo de hejtado is especially easy to understand because the structure is very clear.

Because la sistemo refers to a specific system, while hejtado here is being used in a general descriptive sense.

So the sentence is talking about the system, specifically identified in the situation, and then describing what kind of system it is: a system of heating.

In Esperanto, when a noun after de is being used generically like this, it often appears without la.

If you said de la hejtado, that would usually suggest a specific heating process already known from context.

It comes from funkcii, which means to function or to work in the sense of operating properly.

So funkcias means:

• functions
• works
• is working

In this sentence, it means the system is not operating properly.

The ending -as marks the present tense in Esperanto.

So:

• funkcias = works / is working
• funkciis = worked / was working
• funkcios = will work

Esperanto verbs always use the same tense ending regardless of the subject, so:

• mi funkcias
• vi funkcias
• ĝi funkcias

The verb form does not change for person or number.

Because funkcias is already a complete verb by itself.

In English, we often say is working, but Esperanto does not need an extra auxiliary verb here. The simple present tense funkcias already expresses the idea.

You could make a more descriptive form such as estas funkcianta, but that is less direct and usually less natural for a simple statement like this. For ordinary usage, ne funkcias is exactly what you would expect.

In Esperanto, ne normally goes directly before the word or phrase it negates.

So:

• ne funkcias = does not work / is not working

That placement is very regular in Esperanto and is something learners quickly get used to.

If you want to negate the verb, put ne before the verb.

Because there is no direct object.

• La sistemo is the subject of the sentence.
• de hejtado is a prepositional phrase.
• funkcias is an intransitive verb here; it does not take a direct object.

The accusative -n is mainly used for direct objects and for some expressions of direction. Neither of those applies here.

A helpful breakdown is:

• hejtado = hej-ta-do
• funkcias = funk-ci-as

A few key points:

• j sounds like English y
• ej sounds roughly like the vowel in day
• c always sounds like ts

So funkcias sounds roughly like funk-tsi-as.

Stress in Esperanto is always on the second-to-last syllable:

• hejTAdo
• funkCIas