Коли подруги сумують, вони телефонують одна одній увечері.

Here коли means when.

In this sentence, Коли подруги сумують, вони телефонують одна одній увечері, it introduces a time-related clause: When the female friends feel sad, they call each other in the evening.

In some contexts, English might use if where Ukrainian still uses коли, but in a basic sentence like this, when is the most natural reading.

Подруги is the nominative plural form of подруга (female friend).

It is used because подруги is the subject of the clause: they are the ones doing the action.

• singular: подруга = a female friend
• plural nominative: подруги = female friends

Подруг is a different case form, often genitive plural or accusative plural in some contexts, so it would not work as the subject here.

Yes. Подруга means female friend.

So подруги means female friends. If the group were male or mixed, you would more likely see:

• друзі = friends

This sentence specifically refers to women/girls who are friends.

Сумують is the 3rd person plural present tense form of сумувати, which means to be sad, to feel sad, or sometimes to miss someone/something, depending on context.

Here it matches the plural subject подруги:

• я сумую = I feel sad
• ти сумуєш = you feel sad
• вона сумує = she feels sad
• вони сумують = they feel sad

So подруги сумують = the female friends feel sad.

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

So a sentence without вони could still be understood:

• Коли подруги сумують, телефонують одна одній увечері.

But вони is included for clarity or emphasis. It can help make the sentence feel a bit more explicit, especially for learners or in contexts where the speaker wants to restate the subject.

So both are possible, but вони is not wrong or strange here.

Телефонують means they call or more literally they telephone.

It is the 3rd person plural present tense form of телефонувати.

Examples:

• Я телефоную мамі. = I call my mother.
• Вони телефонують друзям. = They call friends.

A useful grammar point: телефонувати usually takes the person called in the dative case, not the direct object pattern used in English.

Одна одній means each other or one another when referring to females.

In this sentence, it shows that the friends call each other.

The basic pattern is:

• один одного / одна одну / одне одного = each other, in forms that change by gender and case
• одна одній is a feminine form used here because подруги are female and because телефонувати requires the dative case

So:

• вони телефонують одна одній = they call each other

Одній is the dative singular feminine form of одна.

That may seem surprising because the whole meaning is plural (each other), but this expression works as a set phrase where the words change form internally.

The important reason for the dative here is the verb телефонувати, which commonly takes the person being called in the dative:

• телефонувати подрузі = to call a female friend
• телефонувати сестрі = to call a sister

So in вони телефонують одна одній, the одній is in the dative because they are calling to one another.

Увечері means in the evening.

Both увечері and ввечері exist and mean the same thing. Ukrainian often alternates у and в for ease of pronunciation and sound flow.

So:

• увечері = in the evening
• ввечері = in the evening

In this sentence, увечері is chosen because it sounds smooth after одній.

Also, увечері functions like an adverbial time expression here, so you can think of it as a fixed phrase meaning in the evening.

Yes, the word order could be changed.

The sentence as given is:

• Коли подруги сумують, вони телефонують одна одній увечері.

This is a very natural order:

1. time/condition clause: Коли подруги сумують
2. main clause: вони телефонують одна одній увечері

Ukrainian word order is more flexible than English because case endings carry a lot of grammatical information.

Possible variations include:

• Увечері, коли подруги сумують, вони телефонують одна одній.
• Коли подруги сумують, увечері вони телефонують одна одній.

The meaning stays close, but the emphasis shifts slightly depending on what comes earlier.

In this sentence, feel sad is usually the best translation.

The verb сумувати often expresses a state or feeling of sadness, melancholy, or emotional longing. Depending on context, it can also mean to miss someone.

So:

• подруги сумують = the female friends feel sad / are sad

If the meaning shown to the learner is about sadness rather than missing someone, then feel sad is a very good choice.

Usually, no. In standard Ukrainian, телефонувати normally takes the person in the dative case, not as a direct object.

So Ukrainian says something closer to:

• I telephone to my friend structurally

Examples:

• Я телефоную братові. = I call my brother.
• Вона телефонує подрузі. = She calls her female friend.

That is why одна одній is built the way it is here.

Because Коли подруги сумують is a subordinate clause introduced by коли.

In Ukrainian, subordinate clauses are normally separated by commas:

• Коли подруги сумують, вони телефонують одна одній увечері.

This is similar to English:

• When the female friends feel sad, they call each other in the evening.

So the comma is standard punctuation here.