Bubny jsou hlasité.

Bubny is the nominative plural of buben.

• singular: buben = drum
• plural: bubny = drums

In this sentence, bubny is the subject, so it appears in the nominative plural form.

Jsou is the 3rd person plural present form of být, which means to be.

Because the subject bubny is plural, the verb also has to be plural:

• buben je = the drum is
• bubny jsou = the drums are

So jsou matches bubny.

The adjective has to agree with the noun it describes.

Here, bubny is:

• plural
• masculine inanimate

So the adjective takes the matching plural form hlasité.

Compare:

• hlasitý buben = a loud drum
• hlasité bubny = loud drums

Even though hlasité comes after jsou, it still agrees with bubny.

It is in the nominative, because it is a predicate adjective used with být.

In other words, Czech says:

• subject in nominative: bubny
• adjective agreeing with the subject: hlasité

So after být, Czech normally uses the adjective in a form that agrees with the subject, not in some special separate form.

It can mean either, depending on context.

Czech has no articles like a, an, or the, so bubny could mean:

• the drums
• drums

You learn which is meant from the situation or surrounding sentences.

This is the neutral, straightforward word order: subject + verb + adjective.

Czech word order is fairly flexible, so other orders are possible for emphasis or contrast. But Bubny jsou hlasité is the most natural basic version.

For a learner, it is a very good default pattern to remember.

A rough pronunciation guide:

• bubny ≈ BOOB-nih
• jsou ≈ ssoh or ysoh depending on style; in normal speech the j is often weak
• hlasité ≈ HLA-see-tay

A few helpful points:

• Czech stress is usually on the first syllable of each word.
• The y in bubny is not like English y in my. It is closer to a short i sound.
• hl at the start of hlasité is pronounced clearly.

You add ne- to the verb:

Bubny nejsou hlasité.

That means The drums are not loud.

With být, negation is formed very regularly:

• je → není
• jsou → nejsou

Yes, hlasité can also be the singular neuter form in other contexts.

For example:

• auto je hlasité = the car is loud

So by itself, hlasité is not enough to tell you whether something is plural or neuter singular. In this sentence, the subject bubny makes it clear that it is plural agreement.

In standard Czech, you normally keep jsou in the present tense.

So:

• correct: Bubny jsou hlasité.
• not standard here: leaving out jsou

Unlike some languages, Czech usually does not drop the present-tense form of to be in ordinary sentences like this.