Spojka je hlasitá.

Because it is an adjective and it must agree with spojka in gender, number, and case.

• spojka is feminine singular nominative
• so the adjective also takes the feminine singular nominative form: hlasitá

Compare:

• hlasitý = masculine singular
• hlasitá = feminine singular
• hlasité = neuter singular / plural in some contexts

So Spojka je hlasitá uses the feminine form because spojka is feminine.

A very common clue in Czech is the noun ending.

Most nouns ending in -a are feminine, and spojka follows that pattern.

So:

• ta spojka = the clutch / the conjunction / the connector depending on context
• adjective with it will usually be in a feminine form:
  • hlasitá spojka
  • nová spojka
  • dobrá spojka

This is a useful pattern, though there are a few exceptions elsewhere in the language.

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

So:

• jsem = I am
• jsi = you are
• je = he/she/it is

In this sentence, je means is:

• Spojka je hlasitá. = The clutch is loud.

In standard Czech, no: in the present tense, the verb být is normally expressed.

So you say:

• Spojka je hlasitá.

Not normally:

• Spojka hlasitá.

Czech usually keeps je in ordinary statements. Leaving it out would sound ungrammatical or very nonstandard in most normal situations.

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

So:

• spojka can mean a clutch, the clutch, or just clutch in a general sense

The exact meaning depends on context, not on an article.

That is very normal in Czech. Learners coming from English often expect an article, but Czech simply does not use one.

The basic neutral word order here is:

• Spojka je hlasitá.

That is the most straightforward way to say it.

But Czech word order is more flexible than English, and different orders can change emphasis:

• Hlasitá je spojka. = emphasizes the clutch
• Je hlasitá spojka. = possible in special contexts, but less neutral

For a beginner, the safest default is:

• subject + je + adjective
• Spojka je hlasitá.

A simple approximation is:

• SPOY-ka ye HLA-si-taa

A few useful points:

• Czech stress is usually on the first syllable of each word:
  • SPOJ-ka
  • YE
  • HLA-si-tá
• j is pronounced like English y
• á is a long vowel, so it is held a little longer than a

So hlasitá is not the same as hlasita; the long á matters.

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

In:

• Spojka je hlasitá.

the thing being described is spojka, so it stays in nominative:

• spojka

And the adjective also matches that nominative form:

• hlasitá

Yes, if you are making it part of a noun phrase.

For example:

• hlasitá spojka = a loud clutch / the loud clutch

But in your sentence, the adjective comes after je because it is a predicate adjective:

• Spojka je hlasitá. = The clutch is loud.

So there are two different structures:

1. hlasitá spojka
   adjective directly describes the noun inside the noun phrase

2. spojka je hlasitá
   the noun is the subject, and the adjective comes after is

It most directly means loud.

Depending on context, English might translate it as:

• loud
• sometimes noisy

But grammatically, in this sentence it is simply the adjective agreeing with spojka. The exact English wording can vary a little depending on what meaning of spojka the context has already established.