La rentgenbildo montras la makzelon.

The -n marks the direct object in Esperanto.

In this sentence:

• La rentgenbildo = the subject, the thing doing the showing
• montras = shows
• la makzelon = the object, the thing being shown

So makzelo becomes makzelon because it is what the X-ray shows.

A very literal breakdown is:

• La rentgenbildo = the X-ray image
• montras = shows
• la makzelon = the jaw

This -n ending is called the accusative.

Because la means the, and Esperanto uses it much like English for definite nouns.

So:

• La rentgenbildo = the X-ray image
• la makzelon = the jaw

Unlike English, Esperanto has:

• a definite article: la
• no indefinite article: there is no separate word for a/an

So:

• rentgenbildo = an X-ray image / X-ray image
• la rentgenbildo = the X-ray image

Montras is the present-tense form of the verb montri, meaning to show.

Esperanto verb endings are very regular:

• -i = infinitive: montri = to show
• -as = present: montras = shows / is showing
• -is = past: montris = showed
• -os = future: montros = will show

So montras tells you the action is in the present.

Because Esperanto very commonly forms compound words by joining roots together.

Here:

• rentgen- = X-ray
• bildo = picture/image

So rentgenbildo literally means something like X-ray image.

This is extremely normal in Esperanto. Instead of using many separate words, Esperanto often builds one clear compound noun.

The main clue is the -n ending.

• la rentgenbildo has no -n, so it is the subject
• la makzelon has -n, so it is the direct object

In English, word order is usually what tells you who does what. In Esperanto, the accusative -n often makes that clear even if the word order changes.

Yes. Because makzelon has the accusative -n, Esperanto can be more flexible with word order than English.

For example, these still mean essentially the same thing:

• La rentgenbildo montras la makzelon.
• La makzelon montras la rentgenbildo.

The first is more neutral and natural for a learner. The second is possible because -n still shows that makzelon is the object.

The dictionary form is makzelo.

Esperanto nouns normally end in -o, so:

• makzelo = jaw
• makzelon = jaw, as a direct object
• makzeloj = jaws
• makzelojn = jaws, as direct objects

A useful rule is: if you see a noun ending in -on, try removing the -n to find the base form.

Because -o is the standard noun ending in Esperanto.

This is one of the most regular parts of the language:

• -o = noun
• -a = adjective
• -e = adverb

So makzelo is clearly a noun just from its ending.

Esperanto has no separate word for a/an, so you would simply leave out la:

Rentgenbildo montras makzelon.

That is the general pattern:

• la = the
• no article = a/an or just a general noun, depending on context

That said, in real usage, whether this sounds natural depends on context. Often people would choose wording based on what exactly they mean.

A rough pronunciation guide is:

RENt-gen-BEEL-do

A few useful points:

• g is always a hard g, like in go
• e is like e in met
• i is like ee in see
• stress in Esperanto usually falls on the second-to-last syllable

So rentgenbildo is stressed on bil: rent-gen-BIL-do

No. Esperanto verbs do not change according to person or number.

So the same present-tense form works with all subjects:

• mi montras = I show
• vi montras = you show
• li montras = he shows
• ili montras = they show

That means montras does not specifically mean singular. It is just the present tense form.

You would add -j for plural, and keep -n on the direct object.

For example:

La rentgenbildoj montras la makzelojn.

Breakdown:

• rentgenbildo = X-ray image
• rentgenbildoj = X-ray images
• makzelo = jaw
• makzelojn = jaws, as direct objects

If a word is both plural and accusative, the ending is -jn.

There are no adjectives in this sentence, but yes—if you added one, it would have to agree with the noun in number and case.

For example:

• La klara rentgenbildo montras la makzelon. = The clear X-ray image shows the jaw.
• La klara rentgenbildo montras la malsanan makzelon. = The clear X-ray image shows the unhealthy jaw.

If the noun is accusative, the adjective also gets -n:

• la malsanan makzelon

This agreement is a very important Esperanto pattern.