Caloriferul este rece.

The -ul at the end is the definite article in Romanian. It means the radiator, not just a radiator.

• calorifer = radiator / a radiator
• caloriferul = the radiator

Unlike English, Romanian usually adds the to the end of the noun instead of putting a separate word before it.

Este is the 3rd person singular form of the verb a fi (to be) in the present tense.

So:

• eu sunt = I am
• tu ești = you are
• el/ea este / e = he/she/it is

Since caloriferul is a singular noun, Romanian uses este:
Caloriferul este rece = The radiator is cold

Yes. E is a very common shorter form of este.

So both are correct:

• Caloriferul este rece
• Caloriferul e rece

The version with e is more common in everyday speech, while este can sound a bit more formal or careful.

Romanian sentence order here is very similar to English:

subject + verb + adjective

• Caloriferul = the radiator
• este = is
• rece = cold

So the structure is literally:

The radiator is cold.

Sometimes adjectives in Romanian change, but rece is one of those adjectives that has the same singular form for both masculine and feminine.

Examples:

• calorifer rece = cold radiator
• apă rece = cold water

But in the plural, it changes:

• calorifere reci = cold radiators
• apele reci = the cold waters

So in this sentence, rece matches the singular noun caloriferul.

Yes. Calorifer is a masculine noun.

You can see that in the definite singular form:

• masculine singular definite often ends in -ul
• calorifer → caloriferul

Because it is singular and masculine, the sentence uses:

• caloriferul = the radiator
• este = is
• rece = cold

A simple English-friendly approximation is:

kah-loh-ree-FEH-rool EH-steh REH-cheh

A few helpful notes:

• c before e is pronounced like ch in chair, so rece sounds roughly like REH-cheh
• r is usually trilled or tapped
• u is like oo in boot, but shorter
• stress in caloriferul falls on fe: caloriFErul

No, not in a normal sentence like this. Romanian usually keeps the verb to be in the present tense.

So you say:

• Caloriferul este rece.

Not normally:

• Caloriferul rece.

Leaving out este would sound incomplete in standard Romanian.

Possibly, but calorifer is the normal everyday Romanian word for a household radiator/heater. Radiator also exists, but it is often associated with things like a car radiator or technical contexts, depending on usage.

So for home heating, caloriferul is usually the most natural choice.

You make it negative by putting nu before the verb:

• Caloriferul nu este rece. = The radiator is not cold.

In everyday speech:

• Caloriferul nu e rece.

In speech, Romanian often makes a yes/no question mainly through intonation:

• Caloriferul este rece? = Is the radiator cold?

You can also hear:

• E rece caloriferul?

Both are understandable, but the first one is the closest direct match to the statement.

The plural is:

• Caloriferele sunt reci. = The radiators are cold.

Breakdown:

• caloriferele = the radiators
• sunt = are
• reci = cold (plural form)

So the sentence changes in three places:

• noun: caloriferul → caloriferele
• verb: este → sunt
• adjective: rece → reci