La ekskurso komenciĝas apud la monto.

La is the Esperanto definite article, equivalent to the in English.

So:

• la ekskurso = the excursion / the outing
• la monto = the mountain

Esperanto has only one definite article: la. It does not change for gender, number, or case.

The ending -o marks a noun in Esperanto.

So:

• ekskurso = a noun meaning excursion / outing / trip
• monto = a noun meaning mountain

This is one of the most basic patterns in Esperanto:

• -o = noun
• -a = adjective
• -e = adverb
• -i = infinitive verb

Ekskurso means an excursion, outing, or sometimes a short trip, especially one taken for pleasure, school, hiking, or visiting a place.

It is a straightforward noun:

• root: ekskurs-
• noun ending: -o

So la ekskurso is the excursion or the outing.

This is a very common question.

• komenci usually means to begin/start something
• komenciĝi means to begin, to start, to get underway

So:

• Mi komencas la lecionon. = I begin the lesson.
• La leciono komenciĝas. = The lesson begins.

In your sentence, la ekskurso is not beginning something else; it is itself beginning. That is why Esperanto uses komenciĝas.

Komenciĝas can be broken down like this:

• komenc- = begin/start
• -iĝ- = become, happen, start happening to itself / become in a state
• -as = present tense

So komenciĝas literally has the idea of becomes begun or starts itself, but in natural English we simply say begins or is starting.

The suffix -iĝ- often makes a verb intransitive or shows a change of state.

It can mean either, depending on context.

Esperanto present tense -as is broader than English. It can cover:

• begins
• is beginning

So La ekskurso komenciĝas apud la monto could be understood as:

• The excursion begins beside the mountain
• The excursion is beginning beside the mountain

Usually the context tells you which sounds more natural.

Apud is a preposition meaning beside, next to, by, or near.

It usually suggests fairly close position.

So:

• apud la monto = beside the mountain / by the mountain / near the mountain

It is often more specific than a vague English near. If you want to emphasize simple nearness in general, Esperanto also has expressions like proksime de.

Because there is no accusative -n needed here.

Monto is the object of the preposition apud, and after a preposition Esperanto normally uses the basic form without -n.

So:

• apud la monto = beside the mountain

The -n ending is mainly used for:

1. direct objects
2. direction toward a place in some expressions

Here the sentence describes location, not motion toward somewhere, so la monto is correct.

Because la ekskurso is the subject of the sentence, not the direct object.

In La ekskurso komenciĝas apud la monto:

• La ekskurso = the subject
• komenciĝas = the verb
• apud la monto = a prepositional phrase showing location

Subjects do not take -n.

No, Esperanto word order is fairly flexible, though this sentence uses the most neutral order:

• La ekskurso komenciĝas apud la monto.

You could also say:

• Apud la monto komenciĝas la ekskurso.

That version puts more focus on the location.

Because Esperanto marks grammar with endings and prepositions, word order can move around more than in English. Still, subject + verb + other information is the most common and easiest order for learners.

A rough pronunciation guide is:

ko-men-CEE-jahs

A few useful points:

• c in Esperanto sounds like ts
• ĝ sounds like the j in jam
• stress is always on the second-to-last syllable

So komenciĝas is divided like this:

ko-men-CI-ĜAS

with the stress on ci.

Not exactly.

Even though it can feel like it begins itself in English, -iĝ- is not the same as using a reflexive pronoun like sin.

It is better to think of -iĝ- as showing that something comes into a state or happens on its own.

So:

• komenci = begin something
• komenciĝi = begin, start, get underway

This is a normal and very common Esperanto pattern, not a strange special case.