La kelnerino salutas nin kaj demandas, ĉu ni jam pretas fari mendon.

Kelnerino means waitress.

It is built like this:

• kelner- = waiter/server
• -in- = female
• -o = noun ending

So:

• kelnero = waiter
• kelnerino = waitress

The ending -in- is a very common way to mark female people or animals in Esperanto.

Because nin means us, while ni means we.

In this sentence, the waitress is greeting us, so nin is the direct object of salutas.

• ni = we
• nin = us

Esperanto marks a direct object with -n.

So:

• La kelnerino salutas nin = The waitress greets us

The ending -as marks the present tense in Esperanto.

So:

• salutas = greets / is greeting
• demandas = asks / is asking

Unlike English, Esperanto does not change the verb ending depending on the subject:

• mi salutas = I greet
• vi salutas = you greet
• ŝi salutas = she greets
• ni salutas = we greet

It is always -as for the present tense.

Here ĉu introduces an indirect yes/no question. In English, that is usually whether or sometimes if.

So:

• demandas, ĉu ni jam pretas... = asks whether we are already ready...

Esperanto uses ĉu for yes/no questions:

• Direct question: Ĉu vi pretas? = Are you ready?
• Indirect question: Mi demandas, ĉu vi pretas. = I ask whether you are ready.

So in this sentence, ĉu shows that the waitress is asking a yes/no question.

Because ĉu means whether / if in the sense of a yes/no question, while se means if in a conditional sense.

Compare:

• Mi demandas, ĉu vi venos. = I ask whether you will come.
• Se vi venos, mi ĝojos. = If you come, I will be happy.

English uses if for both ideas, but Esperanto keeps them separate:

• ĉu = whether
• se = if (condition)

So after demandas, ĉu is the correct choice here.

Because ĉu ni jam pretas fari mendon is a subordinate clause, and Esperanto usually separates subordinate clauses with a comma.

So the structure is:

• La kelnerino salutas nin kaj demandas
• ĉu ni jam pretas fari mendon

That comma is very normal in Esperanto, even if English punctuation might sometimes be looser.

Because pretas is a verb form, not an adjective form.

Esperanto lets a root appear with different endings:

• preta = ready (adjective)
• preti = to be ready (verb)
• pretas = are ready / is ready

So:

• ni jam pretas = we are already ready

If you used the adjective form, you would normally say:

• ni jam estas pretaj

That also means we are already ready.

So both ideas are possible, but this sentence uses the verbal form pretas.

Jam usually means already or by now.

Here it suggests that the speaker may have had some time to look at the menu, and the waitress is asking whether they are ready now.

So:

• ĉu ni jam pretas = whether we are already ready / ready by now

Without jam, the sentence would simply ask whether they are ready. With jam, there is a small sense of timing or progression.

Yes, mendi would also be possible in many contexts.

• fari mendon = make/place an order
• mendi = order

So:

• ĉu ni jam pretas fari mendon
• ĉu ni jam pretas mendi

Both are understandable and natural.

The version with fari mendon is a noun phrase, similar to English make an order or place an order.

Because mendon is the direct object of fari.

In fari mendon:

• fari = to make/do
• mendon = an order

Since the order is the thing being made, it gets the accusative -n.

Compare:

• fari teon = to make tea
• fari demandon = to ask a question / make a question
• fari mendon = to place an order

So the -n is there for the same reason as in nin: it marks the direct object.

Not completely. Esperanto word order is fairly flexible because endings show the grammar clearly.

This sentence uses a very natural, straightforward order:

• La kelnerino salutas nin kaj demandas, ĉu ni jam pretas fari mendon.

That is the most neutral way to say it.

Some parts could move for emphasis, but not everything would sound equally natural. For example:

• La kelnerino nin salutas... is possible, but more marked
• moving jam can change emphasis slightly

So the word order is not rigid, but the version given is the standard and easiest one for learners to follow.