Я купую вишні, хоча сливи дуже стиглі.

Вишні is the accusative plural of вишня.

It is the direct object of купую:
Я купую вишні = I am buying cherries.

A useful point: for many inanimate plural nouns in Ukrainian, the accusative plural looks the same as the nominative plural. So:

• nominative plural: вишні
• accusative plural: вишні

That is why the form does not visibly change here.

Сливи is nominative plural because it is the subject of the second clause:

сливи дуже стиглі = the plums are very ripe

So the sentence has two parts:

• Я купую вишні — I am buying cherries
• хоча сливи дуже стиглі — although the plums are very ripe

Here, сливи is not an object; it is the thing being described.

In Ukrainian, the verb to be is usually not expressed in the present tense in sentences like this.

So:

• сливи дуже стиглі literally looks like plums very ripe
• but it means the plums are very ripe

This is completely normal Ukrainian grammar.

Compare:

• Він лікар. = He is a doctor.
• Вони щасливі. = They are happy.

Хоча means although, though, or even though.

It introduces a concession: something is true, but the main action still happens anyway.

So here:

• Я купую вишні — this is the main action
• хоча сливи дуже стиглі — this gives a contrasting fact

In other words: the plums are very ripe, but despite that, I am buying cherries.

Because хоча introduces a subordinate clause, and Ukrainian normally separates that clause with a comma.

So:

• Я купую вишні, хоча сливи дуже стиглі.

This is similar to English punctuation in sentences with although, though punctuation rules are not always identical between the two languages.

Купую is the 1st person singular present tense of купувати.

It can mean either:

• I buy (habitually / generally), or
• I am buying (right now)

Ukrainian present tense often covers both meanings, and context tells you which one is intended.

Also, купувати is an imperfective verb, so it focuses on the process or repeated action, not on completion.

Yes. Ukrainian often drops subject pronouns because the verb ending already shows the person.

So both are possible:

• Я купую вишні...
• Купую вишні...

Why include Я then?

Usually for one of these reasons:

• emphasis
• contrast
• clarity
• natural rhythm

So Я is not required, but it is perfectly normal.

Стиглі is the plural form of the adjective стиглий = ripe.

It agrees with сливи, which is plural. In Ukrainian, adjectives agree with the noun in:

• gender
• number
• case

Since сливи is plural nominative, the adjective is also plural nominative:

• singular masculine: стиглий
• singular feminine: стигла
• singular neuter: стигле
• plural: стиглі

Дуже means very.

It modifies the adjective стиглі:

• дуже стиглі = very ripe

Дуже does not change form. It is an adverb, so it stays the same regardless of gender, number, or case.

You can use it with many adjectives and adverbs:

• дуже добрий = very good
• дуже швидко = very quickly

Yes. Ukrainian word order is fairly flexible, though different orders can sound more neutral, more emphatic, or more literary.

The given sentence is natural:

• Я купую вишні, хоча сливи дуже стиглі.

But you could also say:

• Хоча сливи дуже стиглі, я купую вишні.

This puts more focus on the contrast first: Although the plums are very ripe, I’m buying cherries.

So the word order can change, but the emphasis changes with it.

Sometimes a similar idea can be expressed with але = but, but it is not exactly the same structure.

Compare:

• Я купую вишні, хоча сливи дуже стиглі.
  = I’m buying cherries, although the plums are very ripe.

• Сливи дуже стиглі, але я купую вишні.
  = The plums are very ripe, but I’m buying cherries.

Both express contrast, but:

• хоча introduces a subordinate concessive clause
• але joins two coordinated clauses

So they are related in meaning, but not interchangeable word-for-word in every structure.

Yes. Ukrainian often distinguishes between two kinds of cherries:

• вишня / вишні — usually sour cherries
• черешня / черешні — usually sweet cherries

In English, both are often just called cherries, so learners sometimes miss this distinction.

So if you see вишні, it often refers specifically to the sour kind.

That is just how many feminine nouns form the plural in Ukrainian.

Both вишня and слива are feminine singular nouns:

• вишня → вишні
• слива → сливи

The exact ending depends on the noun’s stem and spelling rules, but in broad terms this is a normal plural pattern for feminine nouns.

So the plural forms here are not unusual; they are standard dictionary forms for cherries and plums.