Stomatolog leči koren zuba.

It is basically:

• Stomatolog = the subject
• leči = the verb
• koren zuba = the object phrase

So the pattern is subject + verb + object, just like very common English word order.

More literally, koren zuba is root of the tooth, where zuba depends on koren.

Because Serbian often shows a relationship like of the tooth by putting the second noun into the genitive case.

• zub = tooth
• zuba = of the tooth

So:

• koren zuba = root of the tooth

English usually uses either of or a compound noun like tooth root, but Serbian commonly uses this genitive structure.

Yes, koren is the direct object, so it is in the accusative case.

But koren is a masculine inanimate noun, and for many masculine inanimate nouns, the accusative singular looks the same as the nominative singular.

So:

• nominative: koren
• accusative: koren

That is why it looks unchanged.

Leči is the 3rd person singular present tense form of lečiti.

So it agrees with stomatolog, which is singular:

• ja lečim = I treat
• ti lečiš = you treat
• on/ona leči = he/she treats

Here, stomatolog leči means the dentist treats or the dentist is treating, depending on context.

It can mean either one.

In Serbian, the present tense often covers both:

• a general/habitual meaning: treats
• an action happening now: is treating

So without extra context, Stomatolog leči koren zuba could mean either:

• The dentist treats the root of the tooth
• The dentist is treating the root of the tooth

The infinitive is lečiti.

This is an imperfective verb, so it is used for:

• ongoing actions
• repeated actions
• general statements

A common perfective partner is izlečiti, which is more like to cure / heal completely.

So in this sentence, leči is a natural choice because it describes the treatment process, not necessarily a completed result.

Because Serbian has no articles.

So nouns appear without words like a, an, or the:

• stomatolog can mean a dentist or the dentist
• koren can mean a root or the root

Which meaning is intended depends on context.

Yes, you can also say zubar.

• stomatolog = dentist, more formal/technical
• zubar = dentist, more everyday and conversational

So both are possible, but stomatolog sounds a bit more professional or official.

Yes. Serbian word order is more flexible than English because case endings show what each noun is doing.

The most neutral order here is:

• Stomatolog leči koren zuba.

But other orders are possible for emphasis, for example:

• Koren zuba leči stomatolog.

That would sound more marked, with extra focus on koren zuba. A learner should usually stick with the neutral order first.

Yes, sometimes Serbian can also use an adjective-based expression such as zubni koren.

• koren zuba = root of the tooth
• zubni koren = tooth root / dental root

Both are understandable, but koren zuba is a very straightforward and common structure for learners to recognize because it clearly shows the genitive pattern.

Č is pronounced like ch in church.

So:

• leči sounds roughly like LEH-chee

That letter is important because Serbian distinguishes it from some other similar sounds in spelling.

The dictionary forms are:

• stomatolog = dentist
• lečiti = to treat
• koren = root
• zub = tooth

In the sentence, the changed form is:

• zuba = genitive of zub

The verb also appears in a conjugated form:

• leči = he/she/it treats