Koren zuba je na rendgenskom snimku.

Because Serbian uses the genitive case after another noun to show possession or a part-whole relationship.

So:

• koren = root
• zub = tooth
• koren zuba = root of the tooth / the tooth’s root

Here zuba is the genitive singular of zub.

Yes. That is the literal structure.

Serbian very often uses:

• noun + genitive noun

to express ideas that English often expresses with of or ’s.

Examples:

• vrh planine = top of the mountain
• boja zida = color of the wall
• koren zuba = root of the tooth

So this is a very normal Serbian pattern.

Normally, no. Koren zuba is the standard and natural way.

Using od here would sound unnatural for ordinary possession/part-whole meaning. In Serbian, od is more often used for meanings like:

• from
• made of
• sometimes separation/source

So for the root of the tooth, use koren zuba, not koren od zuba.

It is in the locative case.

That is because na can take different cases depending on meaning:

• na + accusative = movement onto/to something
• na + locative = location on/at something

Here there is no movement. The root is there, so Serbian uses na + locative:

• na rendgenskom snimku = on the X-ray image

The basic form is snimak = image / recording / scan / снимak

But after na with a location meaning, the noun goes into the locative singular:

• snimak → snimku

So:

• na snimku = on/in the image

This same pattern happens with many masculine nouns.

Because adjectives in Serbian must agree with the noun they describe in:

• gender
• number
• case

The noun snimku is:

• masculine
• singular
• locative

So the adjective must match it:

• rendgenski snimak = nominative
• na rendgenskom snimku = locative

That is why both words change together.

The dictionary forms are:

• koren = root
• zub = tooth
• biti = to be
• rendgenski = X-ray, radiographic
• snimak = image, scan, recording

And in the sentence they appear as:

• koren = nominative singular
• zuba = genitive singular
• je = 3rd person singular present of biti
• rendgenskom = locative singular masculine
• snimku = locative singular

Je means is.

It is the 3rd person singular present form of biti = to be.

So the structure is:

• Koren zuba = the root of the tooth
• je = is
• na rendgenskom snimku = on the X-ray image

Together: The root of the tooth is on the X-ray image.

In a normal sentence like this, no, it is usually kept.

Serbian sometimes leaves out forms of to be in very informal notes, headlines, or special styles, but in standard full sentences you normally say:

• Koren zuba je na rendgenskom snimku.

Without je, it would sound incomplete in ordinary usage.

Yes, Serbian uses na here, even though English may say either on the X-ray or in the X-ray image, depending on style.

With pictures, screens, documents, and images, Serbian often uses na where English also often uses on:

• na slici = in/on the picture
• na fotografiji = in/on the photo
• na snimku = in/on the image/scan

So na rendgenskom snimku is completely normal Serbian.

Yes, that is often the most natural interpretation in context.

Literally, Serbian says:

• The root of the tooth is on the X-ray image

But in medical or everyday English, that often comes across more naturally as:

• The tooth root is visible on the X-ray
• The root of the tooth can be seen on the X-ray

So the Serbian sentence may sound slightly more literal than the most natural English equivalent.

Yes. Serbian word order is fairly flexible, and changing it often changes the focus rather than the basic meaning.

For example:

• Koren zuba je na rendgenskom snimku.
  Neutral statement.

• Na rendgenskom snimku je koren zuba.
  More emphasis on where it is.

• Koren zuba je na snimku.
  Shorter, if the type of image is already clear.

The original order is perfectly normal.

That’s right: Serbian has no articles like a or the.

So whether something is understood as a tooth, the tooth, an X-ray, or the X-ray depends on context.

In this sentence, context usually makes it definite:

• koren zuba = the root of the tooth
• na rendgenskom snimku = on the X-ray image

English must choose articles; Serbian does not.

Both exist, depending on the standard/region.

• koren is the Ekavian form
• korijen is the Ijekavian form

So this sentence is in an Ekavian variety of Serbian:

• Koren zuba je na rendgenskom snimku.

An Ijekavian-style equivalent would use korijen instead.

Yes. It is a standard and common way to say X-ray image or radiograph.

You may also hear shorter or more conversational versions, such as:

• rendgen
• na rendgenu = on the X-ray

So in everyday speech, someone might also say something like:

• Koren zuba je na rendgenu.
• Koren zuba se vidi na rendgenskom snimku.

But rendgenski snimak is clear, standard, and precise.

Often, yes.

That version means:

• The root of the tooth can be seen on the X-ray image
• The tooth root is visible on the X-ray

It sounds a bit more explicitly natural in many medical or descriptive contexts, because it directly says is visible.

Still, Koren zuba je na rendgenskom snimku is understandable and grammatical; it is just slightly more literal in wording.