Sestava je krátká.

Because krátká has to agree with sestava.

In Czech, adjectives change their endings to match the noun in:

• gender
• number
• case

Sestava is:

• feminine
• singular
• nominative

So the adjective also has to be feminine singular nominative:

• masculine: krátký
• feminine: krátká
• neuter: krátké

That is why krátká is correct here, not krátký.

Je is the 3rd person singular 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 Sestava je krátká, je means is.

It is needed because this is a normal Czech sentence with a subject and a predicate:

• Sestava = the subject
• je krátká = is short

Unlike in some languages, you normally do use být in this kind of sentence in Czech.

Usually, yes. A noun ending in -a is very often feminine in Czech, and sestava is feminine.

That is why it goes with:

• ta sestava
• krátká sestava

But remember that -a is a strong clue, not an absolute rule for every Czech noun. Still, for sestava, feminine is correct.

Sestava can mean several related things depending on context, for example:

• a set
• a lineup
• an assembly
• a configuration
• a routine or sequence

So even if the basic meaning is already given, it is useful to know that this word is somewhat flexible. The best English translation depends on context.

For example:

• in sports, it might mean lineup
• in technology, it might mean setup/configuration
• in gymnastics or dance, it might mean routine

A helpful approximation is:

• Sestava ≈ SE-sta-va
• je ≈ ye
• krátká ≈ KRAAT-kaa

A few key pronunciation points:

• Czech stress is usually on the first syllable of each word.
• j is pronounced like English y in yes.
• á is a long vowel, so it is held a little longer than a.

A rough pronunciation guide: SEH-stah-vah yeh KRAAT-kah

Because Czech does not use articles the way English does.

So:

• sestava can mean a lineup, the lineup, a setup, or the setup
• the exact meaning depends on context

This is very normal in Czech. You do not need to add a separate word for the or a.

Yes. Czech word order is more flexible than English word order.

The neutral order here is:

• Sestava je krátká.

But other orders are possible for emphasis or style, such as:

• Krátká je sestava.
• Krátká sestava. (this is not a full sentence by itself unless used as a label or heading)

Even though Czech allows flexibility, Sestava je krátká is the most straightforward basic sentence.

Normally, no. In a standard full sentence, you need je.

So the normal sentence is:

• Sestava je krátká.

Leaving out je might appear in:

• notes
• headlines
• very informal or poetic language

But for a learner, the safe rule is: keep the verb in this type of sentence.

It is in the nominative case.

Why? Because sestava is the subject of the sentence:

• Sestava je krátká. = The lineup/setup is short.

The subject of a basic statement is usually in the nominative in Czech.

Also, the adjective krátká matches it in the nominative.

It can mean both, depending on context.

Krátký / krátká / krátké can describe:

• something physically short
• something brief in time or duration
• something not very long in a more general sense

So Sestava je krátká could mean:

• the setup is physically short
• the routine is brief
• the list/lineup is short

Context tells you which meaning is intended.

You replace je with není:

• Sestava není krátká.

That means The lineup/setup is not short.

This is a very common pattern:

• je = is
• není = is not

If the noun becomes plural, both the verb and the adjective change.

For example:

• Sestavy jsou krátké.

Here:

• sestavy = plural
• jsou = are
• krátké = short, plural form

So Czech shows agreement in more than one place:

• the noun
• the adjective
• the verb

It is an adjective.

It describes the noun sestava by giving a quality: short.

In this sentence, it is used as part of the predicate:

• Sestava = noun
• je = verb
• krátká = adjective

So grammatically, this is a simple sentence with a linking verb: noun + to be + adjective.