Obojek je červený.

• obojek = collar
• je = is (3rd person singular of být, to be)
• červený = red

Grammatically:

• obojek is the subject.
• je is the verb.
• červený is a predicate adjective, describing the subject after to be.

Because it has to agree with obojek in gender, number, and case.

Here:

• obojek is masculine singular
• the sentence is in the nominative
• so the adjective takes the matching form červený

This is one of the most important features of Czech: adjectives change their endings depending on the noun they describe.

Obojek is masculine inanimate.

That matters because adjective endings depend on gender. For example:

• masculine inanimate: červený obojek
• feminine: červená
• neuter: červené
• plural: červené / červení depending on the noun type

So in Obojek je červený, the masculine singular form červený matches obojek.

In the present tense, Czech normally keeps the verb být (to be) in sentences like this.

So:

• Obojek je červený = correct
• leaving out je here would usually sound wrong in standard Czech

Czech often drops subject pronouns such as on, ona, já, because the verb ending already shows the person, but the verb itself is still needed here.

Good question. In Czech, attributive adjectives usually come before the noun:

• červený obojek = a red collar

But in your sentence, the adjective is not directly attached to the noun inside a noun phrase. It comes after je and works as a predicate:

• Obojek je červený = The collar is red

So:

• červený obojek = adjective before noun
• obojek je červený = adjective after to be

Both are normal; they are just different structures.

Czech does not have articles like English a, an, and the.

So obojek can mean:

• a collar
• the collar

The exact meaning depends on context.

That is completely normal in Czech. Learners often have to get used to understanding definiteness from the situation rather than from a separate word.

Not as fixed as in English.

Obojek je červený is the most neutral and natural order here.

Because Czech has case endings, word order can change for emphasis or style more easily than in English. But not every possible order sounds equally natural in an ordinary beginner sentence.

For a basic statement, stick with:

• Obojek je červený.

That is the safest version to learn first.

A simple approximation:

• obojek ≈ OH-bo-yek
• červený ≈ CHER-veh-nee

A few useful pronunciation notes:

• č sounds like ch in check
• j sounds like English y
• ý is a long ee-like vowel
• stress in Czech is usually on the first syllable

So:

• Obojek
• ČERvený

Yes, in this sentence they would be wrong, because they do not match obojek.

You need the masculine singular form:

• Obojek je červený.

Compare:

• Kočka je červená. = feminine
• Auto je červené. = neuter

So the adjective ending changes with the noun.

The verb je stays the same in singular, but the adjective changes to match the noun.

Examples:

• Kočka je červená. = feminine singular
• Auto je červené. = neuter singular
• Obojky jsou červené. = masculine inanimate plural

Notice:

• singular: je = is
• plural: jsou = are

This is a very useful pattern to practice.

Yes. The form červený is the basic dictionary form you will usually find listed for adjectives.

That dictionary form is typically:

• masculine singular nominative

So when you learn a new adjective, you will often memorize it in this form:

• červený = red
• velký = big
• malý = small

Then you learn how it changes for other genders and cases.

Yes, but that means something different structurally.

• červený obojek = red collar
• Obojek je červený = The collar is red

So:

• one is a noun phrase
• the other is a full sentence

This is a very useful contrast to notice early in Czech.