La caldaia funziona di nuovo, e il termostato torna subito a segnare la temperatura giusta.

In Italian, nouns have grammatical gender, so you have to learn each noun together with its article:

• la caldaia = the boiler → feminine singular
• il termostato = the thermostat → masculine singular

The article must match the noun’s gender and number. There is not always a logical reason, so it is best to memorize the noun with its article from the start.

A useful pattern:

• nouns ending in -a are often feminine: caldaia
• nouns ending in -o are often masculine: termostato

That pattern helps, but it is not a perfect rule.

Italian often uses the simple present where English might use either the simple present or the present continuous.

So:

• La caldaia funziona di nuovo = The boiler is working again / The boiler works again

In natural English, is working again sounds more common here, but in Italian the simple present funziona is completely normal.

Italian does have a progressive form, such as sta funzionando, but it is not necessary here and would often sound less natural.

Di nuovo means again.

So:

• funziona di nuovo = works again
• torna ... a segnare also gives the idea of again, so the sentence strongly emphasizes that things are back to normal

Italian has other ways to say again, such as di nuovo, nuovamente, and sometimes ancora, but di nuovo is very common and natural in everyday speech.

Tornare a + infinitive means to go back to doing something, to resume doing something, or simply to do something again.

So:

• il termostato torna a segnare = the thermostat goes back to showing/indicating

This is a very common structure in Italian:

• tornare a parlare = to start speaking again
• tornare a vivere = to live again / come back to life
• tornare a funzionare = to work again

Here, torna does not mean the thermostat physically returns somewhere. It is an idiomatic verbal construction.

Because tornare in this meaning is followed by a + infinitive.

So the pattern is:

• tornare a fare qualcosa = to go back to doing something

Examples:

• torno a studiare = I go back to studying
• torna a piovere = it starts raining again
• il termostato torna a segnare = the thermostat goes back to showing

You cannot just say torna segnare. The a is required in this construction.

Subito means immediately, right away, or at once.

Here:

• torna subito a segnare = immediately goes back to showing

It tells you how quickly the thermostat returns to normal.

Its placement is flexible, but the version in the sentence is very natural. You may also hear slightly different placements depending on emphasis, but torna subito a segnare is standard and clear.

Yes, segnare has several meanings, and that can be confusing.

Common meanings include:

• to mark
• to note down
• to score
• to indicate/show/read on a measuring device

In this sentence, the last meaning is the important one.

So:

• il termostato segna 20 gradi = the thermostat reads/shows 20 degrees
• segnare la temperatura giusta = to show the correct temperature

This use is very common with instruments and displays:

• l’orologio segna mezzogiorno = the clock shows noon
• il termometro segna 38 = the thermometer reads 38

Both are possible, but they are not always exactly the same in tone.

In Italian, adjectives often come after the noun:

• la temperatura giusta = the right/correct temperature

This is the most neutral and natural order here.

When an adjective comes before the noun, it can sometimes sound more literary, emphatic, or slightly more subjective:

• la giusta temperatura

That version is possible, but in everyday usage la temperatura giusta sounds more straightforward.

Here giusta means something like correct, right, or proper.

So:

• la temperatura giusta = the correct/right temperature

It does not necessarily mean mathematically exact in a strict scientific sense. It means the thermostat is now showing the temperature it is supposed to show.

Depending on context, English might translate it as:

• the right temperature
• the correct temperature
• the proper temperature

Italian often uses the definite article where English sometimes does too and sometimes does not.

Here, la temperatura giusta means the correct temperature, referring to the specific temperature reading that should be shown.

Without the article, temperatura giusta would usually not work as a complete noun phrase in this sentence. Italian normally needs the article here.

So:

• segnare la temperatura giusta = natural
• segnare temperatura giusta = not natural Italian

Italian can often omit subject pronouns like lui, lei, or esso, but here il termostato is not a pronoun: it is the full noun subject.

Repeating it makes the sentence clear and balanced:

• La caldaia funziona di nuovo, e il termostato torna subito a segnare la temperatura giusta.

There are two different subjects:

• la caldaia
• il termostato

So it makes sense to state both explicitly. If you left out il termostato, the second clause would be unclear because the verb torna needs a subject.

Yes. Both are natural, but they emphasize things a little differently.

• La caldaia funziona di nuovo = the boiler is working again
• La caldaia torna a funzionare = the boiler goes back to working / starts working again

The meaning is very similar. The version in your sentence is slightly simpler and more direct in the first clause, while the second clause uses the tornare a + infinitive structure for variation.

The comma is separating two related clauses:

• La caldaia funziona di nuovo
• e il termostato torna subito a segnare la temperatura giusta

In Italian, a comma before e is sometimes used when the clauses are a bit longer or when the writer wants a small pause. It is not always required, but it is acceptable here.

English is often stricter about commas before and, while Italian punctuation can be a little more flexible in cases like this.

Caldaia usually means boiler, especially the appliance that heats water and/or powers a home heating system.

It is more specific than a general English word like heater.

Depending on context:

• caldaia = boiler
• riscaldamento = heating / heating system
• stufa = stove / space heater

So in this sentence, caldaia is best understood as boiler.

Not really. Subito is stronger than soon.

• subito = immediately / right away
• presto = soon / early

So:

• torna subito a segnare = it immediately starts showing again
• torna presto a segnare would mean something more like it will show correctly again soon

In your sentence, subito suggests the thermostat corrects itself very quickly.

In strict technical terms, a thermostat controls temperature, while a thermometer measures it. But in everyday language, people may refer to the home temperature-control device as a termostato, even if it also has a display.

So in normal Italian usage, this sentence is perfectly believable:

• il termostato torna subito a segnare la temperatura giusta

If you wanted to focus purely on measurement, termometro could also appear in another context, but termostato is natural here for a home heating system.