Klávesnice je důležitou součástí.

Součást is the dictionary form. In this sentence, it becomes součástí because it is in the instrumental singular.

After být (to be), Czech often uses the instrumental for the noun that describes what something is, especially when expressing a role, function, or category:

• Je učitelem. = He is a teacher.
• Je problémem. = It is a problem.
• Je důležitou součástí. = It is an important part.

So součástí is the instrumental form of součást.

Because adjectives in Czech must agree with the noun they describe in gender, number, and case.

Here, důležitou describes součástí, so it has to match it:

• noun: součástí = feminine, singular, instrumental
• adjective: důležitou = feminine, singular, instrumental

That is why you get:

• důležitá součást = an important part (nominative)
• důležitou součástí = an important part (instrumental, as used here)

It does mean is, but Czech grammar often uses the instrumental case after být when the complement is a noun phrase describing what something is.

So in English you simply say:

• The keyboard is an important part.

But in Czech, the noun phrase after je is often put into the instrumental:

• Klávesnice je důležitou součástí.

This is very common and natural in Czech. For a learner, it is useful to remember that after forms of být, a noun describing identity, role, or function is often instrumental.

Klávesnice is in the nominative singular because it is the subject of the sentence.

It is the thing that is something:

• Klávesnice = the keyboard
• je = is
• důležitou součástí = an important part

So the basic structure is:

• subject: klávesnice
• verb: je
• complement: důležitou součástí

Yes, klávesnice is a feminine noun.

That matters when you later use adjectives or pronouns with it. For example:

• ta klávesnice = that keyboard
• nová klávesnice = a new keyboard

In this sentence, however, the adjective důležitou does not agree with klávesnice. It agrees with součástí, because that is the noun it directly modifies.

Czech does not have articles like a, an, or the.

So a sentence like this can often be translated in different ways depending on context:

• The keyboard is an important part.
• The keyboard is the important part.

In most contexts here, the natural meaning is an important part.

Czech usually leaves definiteness and indefiniteness to context rather than marking it with articles.

Often yes. In real usage, součást is very commonly followed by a noun in the genitive to say what whole something belongs to.

For example:

• Klávesnice je důležitou součástí počítače. = The keyboard is an important part of the computer.
• Je součástí systému. = It is part of the system.

In your sentence, that extra information is simply omitted because the context probably already makes it clear.

Yes. Czech word order is fairly flexible because the case endings show the grammatical relationships.

The given order:

• Klávesnice je důležitou součástí.

is the most neutral.

But you could also say:

• Důležitou součástí je klávesnice.

This sounds more emphatic, as if you are highlighting the keyboard in contrast with something else.

So the meaning stays similar, but the emphasis changes.

In standard Czech, Klávesnice je důležitou součástí is the natural form here.

Using the instrumental after je is the normal choice with this kind of predicate noun. So:

• je důležitou součástí = natural, standard, expected

The nominative version je důležitá součást would sound wrong or at least very unnatural in this sentence.

Roughly: KLAA-ves-ni-tseh

A few helpful points:

• á is a long a
• stress in Czech is usually on the first syllable
• c is pronounced like ts

So klávesnice has first-syllable stress, and the last part sounds like -tse.

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

Since klávesnice is singular, the verb must also be singular:

• klávesnice je = the keyboard is

If the subject were plural, you would use jsou:

• Klávesnice a myš jsou důležitými součástmi. = The keyboard and mouse are important parts.

So je is used simply because the subject is singular.