La terapiisto komencas fizioterapion.

Because terapiisto has the noun ending -o and does not have the accusative ending -n, so it is the subject: the person doing the action.

In this sentence:

• La terapiisto = the therapist
• komencas = starts / begins
• fizioterapion = physiotherapy

So the therapist is the one who starts something.

The -n is the accusative ending. In Esperanto, this usually marks the direct object, meaning the thing directly affected by the verb.

Here, fizioterapion is what the therapist starts, so it gets -n:

• fizioterapio = physiotherapy
• fizioterapion = physiotherapy as the direct object

This is one of the most important patterns in Esperanto.

Komencas is the present tense form of the verb.

Esperanto verb endings are very regular:

• -i = infinitive, to start
• -as = present, starts / is starting
• -is = past, started
• -os = future, will start

So:

• komenci = to start
• komencas = starts / is starting

La means the.

So:

• la terapiisto = the therapist

Esperanto has only one definite article, la, and it does not change for gender, number, or case. It always stays la.

In this sentence, it tells us we are talking about the therapist, not just a therapist.

Esperanto normally has no indefinite article. English uses a or an, but Esperanto usually just uses the noun by itself.

So:

• terapiisto = therapist / a therapist
• la terapiisto = the therapist

If Esperanto leaves out la, the meaning is often more general or indefinite.

The suffix -isto usually means a person who works in, practices, or is professionally connected with something.

Examples:

• arto = art → artisto = artist
• scienco = science → sciencisto = scientist
• terapio = therapy → terapiisto = therapist

So terapiisto literally means a therapy professional / therapist.

Terapio means therapy in general.

Fizioterapio is a more specific kind of therapy:

• fizi- relates to the physical body
• terapio = therapy

So fizioterapio means physiotherapy / physical therapy.

The word is built very transparently, which is common in Esperanto.

Yes, Esperanto word order is fairly flexible because the -n ending helps show what is the object.

The normal order here is:

• La terapiisto komencas fizioterapion.

But Esperanto could also allow:

• Fizioterapion komencas la terapiisto.

That still means The therapist starts physiotherapy, because fizioterapion has -n, so it is still the object.

However, the original order is the most neutral and natural for learners.

It can mean either, depending on context.

Esperanto present tense -as often covers both simple present and present progressive meanings that English separates:

• komencas = starts / is starting

So this sentence could be understood as:

• The therapist starts physiotherapy
• The therapist is starting physiotherapy

The exact nuance depends on the situation.

A helpful approximate pronunciation is:

lah teh-rah-pee-EE-stoh koh-MEN-tsahs fee-zee-oh-teh-rah-pee-ON

A few useful pronunciation points:

• c is pronounced like ts
• j sounds like English y
• stress is always on the second-to-last syllable

So:

• terapiisto → te-ra-pi-IS-to
• komencas → ko-MEN-cas
• fizioterapion → fi-zi-o-te-ra-pi-ON

Because la never changes. It is always just la.

In Esperanto, case endings go on the noun, and if there are adjectives, they also match. But the article stays the same:

• la terapiisto
• la fizioterapio
• la fizioterapion

Only the noun changes here, not la.

Not usually in this sentence. Here fizioterapion is being used as an activity or treatment in a general sense, similar to how English might say starts physiotherapy.

If you wanted to talk about one specific session, you would probably use another word such as seanco:

• La terapiisto komencas fizioterapian seancon.
• The therapist starts a physiotherapy session.

So in the original sentence, fizioterapion is best understood as the treatment or practice itself, not one countable session.

Because it does not have the plural ending -j.

Esperanto nouns work like this:

• -o = singular noun
• -oj = plural noun
• -on = singular accusative
• -ojn = plural accusative

So:

• fizioterapio = physiotherapy
• fizioterapion = physiotherapy as a singular direct object

If it were plural, it would be fizioterapiojn, though that would be unusual with this particular word.