Кишківник довгий.

In Ukrainian, the present-tense copula to be is usually omitted in simple statements.

So:

• Кишківник довгий = The intestine is long
• literally, it looks like intestine long

This is completely normal Ukrainian. English requires is, but Ukrainian usually does not in the present tense.

Кишківник is in the nominative singular.

That is the basic dictionary form of the noun, and it is used here because кишківник is the subject of the sentence.

So grammatically:

• кишківник = subject
• довгий = description of that subject

Because the adjective has to agree with the noun.

Кишківник is:

• masculine
• singular
• nominative

So the adjective also appears in the masculine singular nominative form:

• довгий

If the noun changed, the adjective would change too. For example:

• артерія довга = the artery is long
• слово довге = the word is long
• нерви довгі = the nerves are long

Usually, no—not if you want the same sentence meaning.

There is an important difference:

• Кишківник довгий = The intestine is long
  This is a full sentence.
• Довгий кишківник = a long intestine
  This is a noun phrase, not the same sentence structure.

So in this example, word order changes the function:

• noun + adjective = predicative meaning, like is long
• adjective + noun = attributive meaning, like long intestine

This is a very common and important pattern in Ukrainian.

A helpful approximation is:

kysh-KIV-nyk DOV-hyy

A few key points:

• кишкі́вник — the stress is on -ків-
• довги́й — the stress is on the last syllable
• Ukrainian г is not a hard English g; it sounds more like a soft voiced h

So:

• кишкі́вник
• довги́й

If you want to sound more natural, pay attention to the stress more than to making every consonant perfect.

Yes. Кишківник is a singular noun.

Ukrainian often uses a singular anatomical term where English may prefer a plural expression such as intestines or bowels.

So even if the English meaning shown to the learner is plural-like, the Ukrainian word here is grammatically singular, and that is why the adjective is also singular:

• кишківник довгий

Yes, it is grammatically natural.

It sounds like a simple descriptive statement, something you might see in:

• anatomy
• biology
• medicine
• educational materials

By itself, it is a bit context-free, but it is still perfectly normal Ukrainian.

In real-life usage, you might more often hear something slightly more specific, for example:

• У людини кишківник довгий.
• Кишківник у цієї тварини довгий.

But Кишківник довгий is still a correct and natural sentence.

The adjective would change to match the noun.

Compare:

• masculine: кишківник довгий
• feminine: вена довга
• neuter: слово довге
• plural: кишки довгі

So the form довгий is not fixed by itself. It depends on the noun it describes.

That is one of the most important things to notice in this sentence: Ukrainian adjectives agree with the noun in gender, number, and case.