Radiátor je studený.

to be

Breakdown of Radiátor je studený.

• studený: cold
• radiátor: the radiator

Questions & Answers about Radiátor je studený.

Why is there no word for the before radiátor?

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.

What does je do here?

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.

Why is it studený and not studená or studené?

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.