Predavač će objasniti gradivo.

Će is the future-tense auxiliary here. It helps form Future I, the basic Serbian future tense.

So:

• Predavač = subject
• će objasniti = will explain
• gradivo = object

In other words, će is the part that corresponds to English will.

Because after the future auxiliary ću, ćeš, će, ćemo, ćete, će, Serbian often uses the infinitive.

So the pattern is:

• ja ću objasniti
• ti ćeš objasniti
• on/ona/ono će objasniti

That is why you do not say Predavač će objašnjava here.

This is about aspect, which is very important in Serbian.

• objasniti = perfective
  It presents the action as a complete whole: to explain / to finish explaining
• objašnjavati = imperfective
  It presents the action as ongoing, repeated, or in progress: to be explaining / to explain repeatedly

In this sentence, objasniti is natural because the speaker is talking about one completed future action: the lecturer will explain the material.

Compare:

• Predavač će objasniti gradivo.
  = The lecturer will explain the material.
• Predavač će objašnjavati gradivo sat vremena.
  = The lecturer will be explaining the material for an hour.

Gradivo is in the accusative, because it is the direct object of the verb objasniti.

The lecturer will explain what?
→ gradivo

The reason it looks unchanged is that gradivo is a neuter singular noun, and for many neuter nouns:

• nominative singular = accusative singular

So:

• gradivo = nominative
• gradivo = accusative

That is completely normal.

Gradivo usually means material to be studied or taught, such as:

• lesson material
• course material
• subject matter
• content

It is commonly used in school and university contexts.

So depending on context, English translations could be:

• the material
• the course material
• the subject matter

Because Serbian has no articles.

English needs words like:

• a lecturer
• the lecturer
• the material

Serbian usually does not mark that difference with separate words. Context tells you whether something is definite or indefinite.

So Predavač će objasniti gradivo can mean:

• The lecturer will explain the material
• sometimes, depending on context, A lecturer will explain the material

In most real situations, the surrounding context makes the intended meaning clear.

Because će is a clitic. In Serbian, clitics usually go in second position in the clause.

That is why the neutral order is:

• Predavač će objasniti gradivo.

Not normally:

• Će predavač objasniti gradivo.

So a useful thing to remember is:

• the clitic će usually comes after the first word or phrase

This is one of the most important Serbian word-order patterns.

Because Serbian can express this future in two common ways, depending on word order.

You can have:

• Predavač će objasniti gradivo.

But if the infinitive comes before the clitic, it is often written together:

• Objasniće gradivo predavač.

So:

• će objasniti = auxiliary first
• objasniće = verb moved before the clitic, and the forms combine in writing

The meaning is basically the same, but the word order changes the emphasis.

Yes. Serbian word order is more flexible than English word order.

The neutral sentence is:

• Predavač će objasniti gradivo.

But you may also see different orders for emphasis, such as:

• Gradivo će objasniti predavač.
  Emphasis on the material
• Predavač će gradivo objasniti.
  A marked or stylistic order
• Objasniće gradivo predavač.
  Emphasis on the action or a different sentence rhythm

The important thing is that the clitic će still follows the Serbian clitic-position rules.

Not exactly.

Predavač means lecturer or someone who gives lectures/presents.

It is related to predavanje = lecture.

It is not always the same as:

• profesor = professor / sometimes teacher
• nastavnik = teacher, instructor
• učitelj = primary-school teacher

So predavač focuses on the role of delivering a lecture.

This sentence has both sounds:

• predavač has č
• će has ć

A rough guide:

• č = a harder ch sound, somewhat like ch in chocolate
• ć = a softer sound, something like a very soft ty/ch sound

They are different sounds in Serbian, and native speakers hear the difference clearly.

Also:

• j in objasniti is pronounced like English y
• so objasniti sounds roughly like ob-yas-ni-ti

These English approximations are not perfect, but they are a useful starting point.

Yes, in Serbian that is also possible, especially in everyday speech.

So both of these can occur:

• Predavač će objasniti gradivo.
• Predavač će da objasni gradivo.

The version with the infinitive, će objasniti, is very standard and a good form to learn first.

The će da + present-tense form pattern is also very common in Serbian, especially in spoken language.