Kancelářská židle je ergonomická.

Because it is an adjective agreeing with židle, which is feminine singular. In Czech, adjectives change their endings to match the noun’s gender, number, and case.

• masculine singular: kancelářský
• feminine singular: kancelářská
• neuter singular: kancelářské

Since židle is feminine singular, kancelářská must also be feminine singular.

Židle is a feminine noun in Czech. This is something you learn together with the noun, because grammatical gender is part of the word.

A learner might expect feminine nouns to end in -a, but many feminine nouns do not. Židle is one of those feminine nouns ending in -e.

You can also see its gender from the adjectives around it:

• kancelářská
• ergonomická

Both are feminine forms, so they confirm that židle is feminine.

It is in the nominative singular.
In this sentence, židle is the subject, and subjects are normally in the nominative case.

So:

• židle = nominative singular
• kancelářská = adjective agreeing with it in nominative singular
• ergonomická = also nominative singular, agreeing with the subject

Because it describes the subject židle. In Czech, even after the verb být (to be), the adjective still agrees with the noun.

So:

• židle je ergonomická = the chair is ergonomic

If the noun changed, the adjective would change too:

• stůl je ergonomický = the desk/table is ergonomic
• křeslo je ergonomické = the armchair is ergonomic

Je is the 3rd person singular form of být (to be), meaning is.

In standard Czech, you normally do use this verb in sentences like this:

• Židle je ergonomická.

Unlike in some languages, you do not usually leave it out in the present tense.

What Czech often leaves out is the subject pronoun, not the verb:

• Ona je ergonomická would usually just be Je ergonomická, if the subject is already understood.

Czech has no articles. There is no direct equivalent of English a/an or the in ordinary usage.

So Kancelářská židle je ergonomická could mean:

• The office chair is ergonomic
• An office chair is ergonomic
• Office chairs are ergonomic would need a plural form, so not this exact sentence, but context matters in Czech

The exact meaning depends on the situation and context.

Yes. In normal Czech word order, adjectives usually come before the noun:

• kancelářská židle
• velký dům
• nová kniha

That is the standard position. Putting the adjective after the noun is uncommon in ordinary sentences and usually sounds poetic, formal, or specialized.

No, Czech word order is fairly flexible, but different orders sound more or less natural depending on emphasis.

The neutral order is:

• Kancelářská židle je ergonomická.

You could also say:

• Ergonomická je kancelářská židle.

But that sounds more marked, as if you are emphasizing ergonomická or contrasting this chair with something else.

So for a basic statement, the original order is the best one to learn first.

A rough English-friendly approximation is:

kan-tse-LAHRZH-skaa ZHID-leh yeh er-go-NO-mee-tskaa

A few useful notes:

• c is pronounced like ts
• ž sounds like the s in measure
• j is pronounced like English y
• í is a long ee
• á is a long a
• č would sound like ch in chair, though it does not appear in this sentence

The trickiest part for many learners is ř in kancelářská. It is a special Czech sound, something like a rolled or buzzing rzh. You do not need perfect ř immediately to be understood.

They are:

• kancelářský = office, office-related
• židle = chair
• být = to be
• ergonomický = ergonomic

In the sentence, two adjectives appear in the feminine singular form:

• kancelářská from kancelářský
• ergonomická from ergonomický

And je is the present-tense form of být.

No. That would be incorrect, because ergonomický is the masculine form.

Since židle is feminine, you need the feminine adjective:

• Kancelářská židle je ergonomická.

Compare:

• Ten stůl je ergonomický. = masculine
• Ta židle je ergonomická. = feminine
• To křeslo je ergonomické. = neuter

This kind of agreement is one of the most important patterns in Czech grammar.