يتناوب أصدقائي.

Because the sentence uses verb–subject order:

يتناوب أصدقائي

In Modern Standard Arabic, when the verb comes first and the subject is a plural noun after it, the verb is often singular and agrees mainly in gender, not in full number.

So this is normal Arabic. Even though أصدقائي means my friends, the verb stays يتناوب rather than يتناوبون.

Yes. That is also correct.

• يتناوب أصدقائي = verb first
• أصدقائي يتناوبون = subject first

When the subject comes first, the verb usually shows full agreement, so you get يتناوبون.

The difference is mostly about word order and emphasis:

• يتناوب أصدقائي sounds more neutral and very standard in formal Arabic.
• أصدقائي يتناوبون puts more focus on my friends.

The -ي means my.

So:

• أصدقاء = friends
• أصدقائي = my friends

This is a possessive suffix attached directly to the noun.

Because a noun with a possessive suffix is already definite.

So Arabic says:

• أصدقائي = my friends

and not:

• الأصدقائي

The suffix -ي already makes the noun specific.

The dictionary form is the past tense verb تناوبَ.

Its present tense is يتناوبُ.

This verb is from Form VI in Arabic morphology. Form VI often gives a sense of:

• mutual action
• reciprocal action
• people doing something with each other or in alternation

That fits this verb well, because taking turns is naturally a reciprocal action.

Usually, the verb itself already suggests that idea.

So يتناوب أصدقائي naturally means that your friends are taking turns among themselves or alternating.

You do not need to add another word unless you want to be more explicit. For example, you could add details about what they are taking turns doing.

Not necessarily.

This verb can be used without a direct object when the meaning is simply that people are taking turns or alternating.

If you want to say what they are taking turns doing, you can add a phrase, for example:

• يتناوب أصدقائي على القراءة = my friends take turns reading
• يتناوب أصدقائي في الكلام = my friends take turns speaking

So the short sentence is complete on its own.

It is the subject, so it is nominative in function.

However, in normal unvowelled writing, that case is not clearly visible here. This is very common in Arabic: learners often need to understand the grammar from the sentence structure, not just from the written ending.

So even if you do not see a clear case ending, أصدقائي is still functioning as the nominative subject.

A common pronunciation guide is:

yatanāwabu aṣdiqāʾī

A few helpful notes:

• يتناوب = ya-ta-naa-wa-bu
• أصدقائي has a hamza sound before the final -ī
• the last word is roughly aṣ-di-qaa-ʾee

So the sentence has a smooth rhythm: yatanāwabu aṣdiqāʾī

Grammatically, أصدقائي is a masculine plural form, but in Arabic that can also be used for a mixed group.

So it can mean:

• male friends
• a mixed group of male and female friends

If you specifically mean female friends, you would normally use صديقاتي.

Then the sentence would change, for example:

• تتناوب صديقاتي = my female friends take turns
• صديقاتي يتناوبن = my female friends take turns

Yes, if the subject is already understood from context.

• يتناوبون = they take turns

This is different from يتناوب أصدقائي because now the subject is not a separate noun after the verb; instead, it is built into the verb ending -ون.

So:

• يتناوب أصدقائي = my friends take turns
• يتناوبون = they take turns

Both are correct, but they are used in slightly different situations.