Večeras ću poslati poruku sestri.

Ću is the 1st person singular future auxiliary, meaning I will.

In Serbian, the future tense is often formed with:

• a form of hteti (to want / will as an auxiliary)
• • the infinitive of the main verb

So in this sentence:

• ću = I will
• poslati = send

Together, ću poslati means I will send.

Because Serbian usually does not need a subject pronoun if the verb already shows who the subject is.

Here, ću already tells you the subject is I.

So:

• Večeras ću poslati poruku sestri. = Tonight I will send a message to my sister.

You could also say:

• Ja ću večeras poslati poruku sestri.

But ja is usually added only for emphasis, contrast, or clarity.

Because ću is a clitic, and clitics in Serbian normally go in the second position of the clause.

That is why you get:

• Večeras ću poslati poruku sestri.

The first element is Večeras, and then the clitic ću comes right after it.

This is very normal in Serbian. Compare:

• Ja ću poslati poruku sestri.
• Sutra ću doći.
• Mojoj sestri ću poslati poruku.

In each case, ću tends to appear after the first stressed element.

Yes. That is also correct.

Serbian has another very common way to express the future:

• poslaću = I will send

This is essentially the future auxiliary attached to the verb.

So these are both natural:

• Večeras ću poslati poruku sestri.
• Večeras poslaću poruku sestri. (less common in this exact order)
• Poslaću poruku sestri večeras.

However, Večeras ću poslati... is especially natural because the clitic ću sits in second position.

Because poslati is the perfective verb, meaning a completed sending: one whole act of sending.

In Serbian, aspect matters a lot:

• slati = imperfective, to send / to be sending / to send repeatedly
• poslati = perfective, to send (successfully, as one completed act)

In a sentence like Tonight I will send a message, Serbian usually prefers the perfective verb because the action is seen as one completed event:

• Večeras ću poslati poruku...

If you used the imperfective, it would sound different in meaning or style.

Because poruku is in the accusative case.

It is the direct object of the verb poslati—the thing being sent.

Base form:

• poruka = message (nominative)

In this sentence:

• poruku = accusative singular

So:

• poslati poruku = to send a message

This is a very common pattern with feminine nouns ending in -a:

• nominative singular: poruka
• accusative singular: poruku

Because sestri is in the dative case.

The dative is used for the recipient—the person to whom something is given, sent, said, shown, etc.

Base form:

• sestra = sister

In this sentence:

• sestri = to the sister / to my sister

So:

• poslati poruku sestri = send a message to my sister

This is a very important Serbian pattern:

• dati knjigu bratu = give a book to the brother
• pisati prijatelju = write to a friend
• poslati poruku sestri = send a message to my sister

Because Serbian often expresses meanings like to someone through case endings, not through a separate preposition.

In English, you say:

• to my sister

In Serbian, the idea of to is built into the dative ending:

• sestri

So Serbian does not need a separate word equivalent to English to in this sentence.

Večeras means tonight or this evening, depending on context.

It is an adverb of time, and it tells you when the action will happen.

Examples:

• Dolazim večeras. = I’m coming tonight.
• Večeras ću učiti. = Tonight I’ll study.

It is a fixed time expression, so you just learn it as a whole word.

Yes. Serbian word order is fairly flexible, and changing it often changes the focus or emphasis, not the basic meaning.

For example:

• Večeras ću poslati poruku sestri.
  Focuses naturally on tonight.

• Poruku ću večeras poslati sestri.
  Puts more attention on the message.

• Sestri ću večeras poslati poruku.
  Puts more attention on to my sister.

The cases show who is doing what to whom, so Serbian can move words around more freely than English.

In this sentence by itself, sestri literally means to the sister or to sister, depending on context.

But in natural translation, English often uses my sister because that is what sounds most natural in many contexts.

If Serbian wants to say to my sister explicitly, it can say:

• mojoj sestri

So:

• Večeras ću poslati poruku sestri. = Tonight I will send a message to my sister / to my sister-like understood sister
• Večeras ću poslati poruku mojoj sestri. = Tonight I will send a message to my sister (explicit)

Serbian often leaves possession implied when it is obvious from context, especially with family members.

A simple pronunciation guide would be:

• Večeras = VE-che-ras
• ću = roughly choo
• poslati = pos-LA-ti
• poruku = po-RU-ku
• sestri = SES-tri

A rough full pronunciation:

• VE-che-ras choo pos-LA-ti po-RU-ku SES-tri

A few helpful sounds:

• č sounds like ch in church
• ć is also similar to ch, but softer
• r is rolled or tapped

Yes. It is completely natural and idiomatic.

A Serbian speaker would easily understand it as a normal everyday sentence meaning:

• Tonight I’ll send my sister a message.

It is a good example of several important Serbian features at once:

• future tense with ću
• clitic second position
• accusative poruku
• dative sestri
• flexible but natural word order