La okcidenta ĉambro estas granda.

Because -a is the normal adjective ending in Esperanto.

So:

• okcidento = west (a noun)
• okcidenta = western (an adjective)

In this sentence, okcidenta describes ĉambro, so it has to be an adjective.

Because they are both adjectives:

• okcidenta describes which room
• granda describes what the room is like

In Esperanto, adjectives take -a and agree with the noun in number and case.

Here, ĉambro is singular and not accusative, so both adjectives stay in the basic form:

• okcidenta ĉambro
• estas granda

If the noun were plural, you would get:

• La okcidentaj ĉambroj estas grandaj.

La is the definite article, meaning the.

It does not change for:

• singular or plural
• gender
• case

So Esperanto always uses the same form: la.

In this sentence, la shows that we are talking about a specific room, not just any western room.

Estas is the present-tense form of esti, which means to be.

So:

• mi estas = I am
• vi estas = you are
• li/ŝi estas = he/she is
• ili estas = they are

Unlike English, Esperanto does not change the verb form depending on the subject. Estas always means present tense, no matter who or what the subject is.

Because Esperanto verbs do not agree with the subject in number or person.

That means:

• La ĉambro estas granda.
• La ĉambroj estas grandaj.

In both sentences, the verb is still estas.

Only the noun and adjective change for plural, not the verb.

Yes. Esperanto allows adjectives either before or after the noun.

So both are possible:

• la okcidenta ĉambro
• la ĉambro okcidenta

But putting the adjective before the noun is usually the more neutral and common choice, especially for everyday description.

So La okcidenta ĉambro estas granda sounds completely normal.

Yes, Esperanto word order is fairly flexible.

The neutral order here is:

• La okcidenta ĉambro = subject
• estas = verb
• granda = predicate adjective

You could change the order for emphasis, for example:

• Granda estas la okcidenta ĉambro.

That is grammatical, but less neutral. A learner should usually start with the standard order used in your sentence.

Because Esperanto often prefers a simple adjective when English would use one too.

• okcidenta ĉambro = western room
• ĉambro de la okcidento would mean something more like room of the west, which is less natural in this situation

So when you want to describe a noun with a quality or location-type adjective, the -a form is usually the normal choice.

Ĉ is pronounced like ch in church.

So:

• ĉambro sounds roughly like CHAM-bro

A few other useful comparisons:

• c = ts as in cats
• ĉ = ch as in child

That difference is important in Esperanto, because they are different letters.

In Esperanto, the stress is almost always on the second-to-last syllable.

So here:

• okcidenta → ok-ci-DEN-ta
• ĉambro → ĈAM-bro
• estas → ES-tas
• granda → GRAN-da

This stress rule is very regular, which makes pronunciation easier than in English.

Because it describes the noun, not the action.

• granda = adjective, used for nouns
• grande = adverb, used for verbs, adjectives, or whole clauses

Here, the sentence says what the room is, so Esperanto uses the adjective:

• La ĉambro estas granda.

If you used grande, that would be wrong here.

You would change the noun and the adjectives to plural by adding -j:

• La okcidentaj ĉambroj estas grandaj.

Changes:

• okcidenta → okcidentaj
• ĉambro → ĉambroj
• granda → grandaj

But the verb stays the same:

• estas stays estas