Radiátor je studený.

Czech has no articles, so there is no direct equivalent of the or a/an in a normal sentence like this.

So:

• radiátor can mean the radiator or a radiator
• the exact meaning depends on context

If you need to be more specific, Czech usually does that through context, word order, or words like ten (that/the one), but in a basic sentence, no article is used.

Je is the 3rd person singular present form of the verb být (to be).

So:

• já jsem = I am
• ty jsi = you are
• on/ona/ono je = he/she/it is

In Radiátor je studený, je means is.

Because studený has to agree with radiátor.

Radiátor is:

• masculine
• singular
• nominative

So the adjective also appears in the matching form:

• masculine singular: studený
• feminine singular: studená
• neuter singular: studené

Examples:

• Polévka je studená. = The soup is cold.
• Pivo je studené. = The beer is cold.

It is in the nominative case, because it is the subject of the sentence.

In this sentence:

• Radiátor = subject
• je = verb
• studený = predicate adjective

A simple way to think of it is: What is cold? → the radiator. That subject is in the nominative.

Because after být (to be), Czech often uses a predicate adjective in the nominative.

So in a sentence like:

• Radiátor je studený
• Dům je velký
• Voda je teplá

the adjective agrees with the subject in gender and number, and it appears in the nominative form.

Yes, but it means something slightly different in structure.

• Radiátor je studený. = The radiator is cold.
• studený radiátor = a cold radiator / the cold radiator

So:

• studený radiátor is a noun phrase
• Radiátor je studený is a full sentence

In Czech, adjectives usually go before the noun when they directly describe it inside a noun phrase.

Yes. Czech word order is more flexible than English, but the neutral order here is:

• Radiátor je studený.

You may also hear or see:

• Studený je radiátor.
• Radiátor studený není. = The radiator is not cold.

Changing the word order usually changes emphasis, not the core meaning. For a learner, the safest default is subject + je + adjective.

A helpful approximation is:

RAH-dee-ah-tor yeh STOO-deh-nee

A few important pronunciation points:

• Czech stress is usually on the first syllable of each word:
  • RAdiátor
  • je
  • STUdený
• j is pronounced like English y in yes
• á is a long a
• ý is a long ee-like sound

The spelling is quite regular, so once you know the sound system, pronunciation becomes much easier than in English.

The mark over ý shows that the vowel is long.

So:

• y = short
• ý = long

In modern Czech pronunciation, y and i are pronounced very similarly, and ý and í are also pronounced very similarly. The difference in spelling is mainly important for:

• grammar
• word forms
• correct writing

So in studený, the final ý is the normal masculine singular adjective ending here.

Yes. In Czech, grammatical gender is not the same as biological sex.

Radiátor is a masculine inanimate noun.

That is why it takes masculine adjective forms such as:

• studený
• nový
• velký

Even though a radiator is an object, it still belongs to a grammatical gender class.

In standard Czech, in a sentence like this, you normally keep je:

• Radiátor je studený.

You may sometimes hear shortened or informal styles where forms of to be are dropped, especially in headlines, notes, or very colloquial speech, but as a learner you should treat je as necessary here.

So the correct standard sentence is:

• Radiátor je studený.

Not in the same way English does.

English often needs a subject pronoun, but Czech usually does not use a dummy subject like it. If you are talking about the radiator, you simply say:

• Radiátor je studený.

If the subject is already clear from context, Czech can also omit pronouns more freely than English, but nouns like radiátor are used normally when needed.

Yes. Studený is the normal everyday word for something physically cold to the touch.

So for objects, food, drinks, or parts of a room, it works very naturally:

• Radiátor je studený.
• Káva je studená.
• Voda je studená.

It is the most straightforward adjective a learner should use in this sentence.