La dentisto preparas plian injekton.

In Esperanto, -o marks a noun. So dentisto means dentist as a noun.

You can also see the useful word-building pattern here:

• dent- = tooth
• -ist- = a person who works with or practices something
• -o = noun ending

So dentisto literally means something like tooth-professional.

La is the Esperanto definite article, meaning the.

So:

• la dentisto = the dentist
• dentisto = a dentist or just dentist, depending on context

A helpful point: Esperanto has only one definite article, la, and it does not change for gender, number, or case.

Preparas comes from the verb prepari, meaning to prepare.

In Esperanto, verbs have very regular endings:

• -as = present tense
• -is = past tense
• -os = future tense
• -us = conditional
• -u = command / wish form
• -i = infinitive

So:

• preparas = prepares / is preparing

The subject does not change the verb form. Whether it is I, you, he, they, etc., the present tense always uses -as.

Because plian describes injekton, and injekton has the ending -n. In Esperanto, adjectives must agree with the nouns they describe.

So if the noun is:

• singular noun: injekto
• singular direct object: injekton

then the adjective must match:

• plia injekto
• plian injekton

This is called agreement.

The -n marks the direct object. That is, it shows what is being prepared.

In this sentence:

• La dentisto = the subject, the one doing the action
• preparas = prepares
• plian injekton = the thing being prepared

So injekton has -n because it is the direct object.

Because dentisto is the subject, not the direct object.

In Esperanto, the -n usually marks the direct object, not the subject.

So here:

• La dentisto = who is doing the action
• plian injekton = what is receiving the action

That is why only plian injekton gets -n.

Plia means additional, another, or one more.

So plian injekton means:

• another injection
• an additional injection
• one more injection

A learner might confuse plia with pli:

• pli = more
• plia = additional / another

For example:

• pli granda = bigger / more large
• plia injekto = an additional injection

Yes, it can go after. Esperanto word order is fairly flexible here.

Both are possible:

• plian injekton
• injekton plian

But putting the adjective before the noun is more common and usually more natural in simple sentences.

No matter where the adjective goes, it still has to agree with the noun:

• plian injekton
• injekton plian

It is essentially an international word adapted to Esperanto spelling and grammar.

Many medical and scientific words in Esperanto come from forms that are familiar across European languages. Here:

• injekto = injection
• injekton = injection as a direct object

This is very common in Esperanto vocabulary.

A rough pronunciation guide is:

lah den-TEE-stoh preh-PAH-rahs PLEE-ahn in-yek-TOHN

A few points:

• e is like e in met
• i is like ee in see
• j sounds like English y
• stress is always on the second-to-last syllable

So:

• den-TIS-to
• pre-PA-ras
• PLI-an
• in-jek-TON

Yes, to some extent. Because -n marks the object, Esperanto allows more flexible word order than English.

For example, these all still show the same basic roles:

• La dentisto preparas plian injekton.
• Plian injekton la dentisto preparas.

The most neutral and common order is still subject–verb–object, which is what your sentence uses.

You would use the plural ending -j, and if it is still a direct object, you also keep -n.

So:

• injekto = injection
• injektoj = injections
• injektojn = injections as a direct object

And the adjective must match:

• pliaj injektoj
• pliajn injektojn

So The dentist prepares additional injections would be:

La dentisto preparas pliajn injektojn.

Because Esperanto normally does not have an indefinite article.

English distinguishes:

• a dentist
• the dentist

Esperanto usually distinguishes only:

• dentisto = a dentist / dentist
• la dentisto = the dentist

So if Esperanto does not use la, the noun is often understood as indefinite or general from context.