Prijaviću se danas.

The dictionary form is prijaviti se.

That is the form you would normally look up in a dictionary. In the sentence Prijaviću se danas, the verb is in the future tense, so it looks different from the dictionary form.

This is future I in Serbian.

It comes from:

• prijaviti se = the infinitive
• ću = I will

So the full underlying idea is:

• Ja ću se prijaviti danas.

In the contracted written form, this becomes:

• Prijaviću se danas.

So -ću here means I will.

Because Serbian often joins the future clitic ću to an infinitive ending in -ti.

So:

• prijaviti + ću → prijaviću

The final -ti drops, and ću attaches to the verb stem.

This is very common in Serbian:

• uraditi → uradiću
• kupiti → kupiću
• prijaviti → prijaviću

A useful extra note: this does not happen the same way with infinitives ending in -ći:

• doći ću, not doću

Se is a reflexive clitic.

It does not always translate literally as myself. In many Serbian verbs, se is just part of the normal verb form.

So:

• prijaviti can mean things like to report or to register something
• prijaviti se means to register/sign up/apply/report oneself, depending on context

In this sentence, se is part of the verb expression, so you generally should learn prijaviti se as a unit.

Because se is an enclitic, which means it usually cannot stand alone or take strong stress. It tends to appear in a fixed position near the beginning of the sentence.

So Prijaviću se danas is natural.

You can also have:

• Danas ću se prijaviti.
• Ja ću se danas prijaviti.

But se normally does not go freely just anywhere.

Yes. All of these are possible:

• Prijaviću se danas.
• Ja ću se prijaviti danas.
• Danas ću se prijaviti.

The difference is mostly word order and emphasis, not basic meaning.

A rough idea:

• Prijaviću se danas. = neutral, with focus on the action
• Danas ću se prijaviti. = emphasizes today
• Ja ću se prijaviti danas. = emphasizes I

Serbian word order is more flexible than English, but clitics like ću and se still follow certain placement rules.

No. Serbian usually drops subject pronouns when they are already clear from the verb form.

In prijaviću, the ending already tells you it is first person singular:

• I will register / I will sign up

So:

• Prijaviću se danas. = perfectly natural
• Ja ću se prijaviti danas. = also correct, but ja adds emphasis or contrast

Because prijaviti se is perfective, and perfective verbs are very common for a single completed future action.

This sentence suggests one complete action:

• I will sign up today
• I will register today

That is exactly the kind of situation where Serbian often prefers a perfective verb.

If you wanted to talk about repeated or ongoing future registration, you would need a different structure or an imperfective idea, depending on the context.

A rough pronunciation guide is:

• pri-ja-vi-ću se da-nas

Helpful notes:

• j sounds like English y in yes
• ć is a soft Serbian sound, somewhat like a softer ch, but not exactly the same
• c and č/ć are different letters in Serbian, so it is worth learning them separately

A rough English-style approximation would be:

• pree-yah-VEE-ću seh DAH-nahs

That approximation is not perfect, but it can help you get started.

Here are the common future forms of prijaviti se:

• prijaviću se = I will sign up / register
• prijavićeš se = you will sign up
• prijaviće se = he/she/it will sign up
• prijavićemo se = we will sign up
• prijavićete se = you all / you formal will sign up
• prijaviće se = they will sign up

Notice that:

• prijaviće se can mean either he/she will sign up or they will sign up
• the subject is usually understood from context

The non-contracted version is:

• Ja ću se prijaviti danas.

This is very useful for learners because it clearly shows the parts:

• ću = will
• se = reflexive clitic
• prijaviti = infinitive

So it can help to think of the sentence in two ways:

• Ja ću se prijaviti danas.
• Prijaviću se danas.

Both are correct; the second is just the contracted form commonly used in Serbian.