Хвіст кота мокрий.

Because кота is the genitive singular form of кіт (cat).

In Хвіст кота мокрий, the structure is literally the tail of the cat is wet. In Ukrainian, possession is often expressed with the genitive case, so кота means of the cat.

• кіт = cat (dictionary form, nominative)
• кота = of the cat

So:

• Хвіст кота = the cat’s tail / the tail of the cat

In the present tense, Ukrainian normally does not use a separate verb for is/am/are in simple statements like this.

So:

• Хвіст кота мокрий literally looks like Tail of-the-cat wet
• but it means The cat’s tail is wet

This is completely normal in Ukrainian. The present-tense to be is usually omitted.

Because мокрий is an adjective in the masculine singular nominative form, and it agrees with хвіст.

• хвіст = masculine singular
• so the adjective describing it must also be masculine singular
• therefore: мокрий

This is called adjective agreement.

Compare:

• мокрий хвіст = wet tail (masculine)
• мокра кішка = wet female cat (feminine)
• мокре хутро = wet fur (neuter)

Because of the grammar.

Хвіст is in the nominative case, which usually marks the main subject of the sentence.
кота is in the genitive case, showing possession: of the cat.

The adjective мокрий is also in the nominative masculine singular, so it matches хвіст, not кота.

So the sentence means:

• [Хвіст] [кота] [мокрий]
• [The tail] [of the cat] [is wet]

Yes. Both are correct translations.

In natural English, the cat’s tail sounds more normal.
But grammatically, Ukrainian is using a structure closer to the tail of the cat.

So:

• Хвіст кота = the cat’s tail
• literally = tail of the cat

Yes, Ukrainian word order is fairly flexible.

Хвіст кота мокрий is a neutral, natural way to say it.

You may also see other orders for emphasis, for example:

• Мокрий хвіст кота = The cat’s tail is wet / The wet tail of the cat
• Кота хвіст мокрий = possible, but marked and less neutral

Because Ukrainian uses case endings, the roles of the words are clearer than in English, so word order can shift more easily. Still, the given order is a standard one.

Yes. Хвіст is a masculine noun.

That matters because adjectives must agree with it:

• хвіст → masculine
• therefore мокрий → masculine

If the noun were feminine or neuter, the adjective ending would change.

A simple learner-friendly pronunciation guide would be:

khveest ko-TA MO-kryy

A few notes:

• х sounds like a throaty kh, not like English h
• і sounds like ee
• кота has stress on the second syllable: коТА
• мокрий has stress on the first syllable: МОкрий

A more careful approximation:

• Хвіст ≈ khveest
• кота ≈ ko-TA
• мокрий ≈ MO-kryy

Ukrainian has no articles.

So a noun like хвіст can mean:

• a tail
• the tail

The exact meaning depends on context.

In this sentence, English naturally uses the cat’s tail is wet, but Ukrainian does not need a separate word for the.

In theory, without articles, Ukrainian can leave that kind of distinction open. But in normal context, Хвіст кота мокрий will usually be understood as a specific tail: The cat’s tail is wet.

If someone wanted to make it more clearly indefinite or general, they would usually rely on context or rephrase the sentence.

So the most natural translation here is:

• The cat’s tail is wet

Yes, but it is slightly different in focus.

• Хвіст кота мокрий = The cat’s tail is wet
  This is a full statement.

• Мокрий хвіст кота = the cat’s wet tail
  This sounds more like a noun phrase by itself, not necessarily a complete sentence.

In speech, Мокрий хвіст кота could sometimes work as a sentence depending on intonation, but the standard clear sentence is Хвіст кота мокрий.

The dictionary forms are:

• хвіст = tail
• кіт = cat
• мокрий = wet

In the sentence, only кіт changes form:

• dictionary form: кіт
• sentence form: кота

That change shows possession: of the cat.