Learn Hardcore Esperanto: La koncerto komenciĝas vespere, sed ni jam sidas en kafejo apud la muzeo. - The concert begins in the evening, but we are already sitting in a café next to the museum.

La koncerto = the concert (a specific concert that speaker and listener know about).
en kafejo = in a café (some café, not specified which one).

So:

Use la when you mean a particular, identifiable thing.
Omit la when you mean something non‑specific (like English a/an), or when you’re talking about things in general.

In this sentence, the concert is a specific event we’ve been talking/thinking about, but the café is just some café near the museum, not yet identified.

What exactly does komenciĝas mean, and how is it different from komencas?

Komenci means to begin / to start.

Esperanto uses the suffix -iĝ- to form intransitive “become / get / start” meanings. So:

komenci = to begin (something), transitive
- Li komencas la koncerton. – He starts the concert.
komenciĝi = to begin / to start (by itself), intransitive
- La koncerto komenciĝas. – The concert starts / is starting.

In the sentence, La koncerto komenciĝas is correct because the concert is beginning; it doesn’t “begin something else”, so an intransitive verb with -iĝ- is used.

Why is present tense komenciĝas used for something that happens in the evening (i.e. in the future)?

Esperanto often uses the present tense for scheduled or very near future events, just like English can:

English: The concert starts this evening. (present form, future meaning)
Esperanto: La koncerto komenciĝas vespere.

You could also say:

La koncerto komenciĝos vespere. – The concert will start in the evening.

Both are grammatically fine. Komenciĝas feels more like a general statement of the schedule (“it starts in the evening as a rule / according to the plan”), while komenciĝos focuses more on the future time.

What is the function of vespere? Why not say en la vespero?

Vespere is the adverb form of vespero (evening):

vespero = evening (noun)
vespere = in the evening / of an evening / evenings (adverb, time)

Using the -e ending is the usual way in Esperanto to express time in a simple, adverbial way:

morgaŭ – tomorrow
hodiaŭ – today
nokte – at night
vespere – in the evening

You can say en la vespero, but:

vespere sounds more natural and general (“in the evening (as the time when it happens)”).
en la vespero is more literally in the evening, referring more explicitly to that time period; it might feel a bit heavier or more specific in this kind of sentence.

So vespere is the normal, concise way to modify the verb with a time expression.

How does jam work here? Does it mean already or now?

In this sentence, jam means already, just like in English:

ni jam sidas = we already sit / we are already sitting.

Core meanings of jam:

already
- Li jam venis. – He has already come.
sometimes by now / yet in contrast with ankoraŭ:
- ĉu vi jam finis? – have you finished already?
- ne, mi ankoraŭ laboras. – no, I’m still working.

So here the idea is: The concert (will) start(s) in the evening, but we are already sitting in a café…

Why does the sentence use ni jam sidas instead of something like ni jam estas sidantaj? Are both correct?

Both are grammatically correct, but they feel different:

ni jam sidas – “we are already sitting.”
- In Esperanto, a simple present tense often covers what English expresses as am/is/are doing.
- This is the normal, neutral way to say it.
ni jam estas sidantaj – literally “we already are sitting (persons).”
- This uses estas + -ant- to form a more “continuous” aspect.
- In practice, Esperanto doesn’t need the continuous form as often as English, so this can sound heavier or more emphatic, as if stressing the ongoing action or state.

In everyday Esperanto, ni jam sidas is preferred and perfectly clear as a present, ongoing state.

Why en kafejo and not en la kafejo? How would the meaning change?

en kafejo = in a café (some café, not identified)
en la kafejo = in the café (a particular café, which speaker and listener know or which was already mentioned)

So:

The sentence as given imagines any café near the museum; its exact identity doesn’t matter.
If you say en la kafejo apud la muzeo, you suggest there is a specific, known café by the museum (maybe the only one there, or one previously introduced in the conversation).

What does the suffix -ejo in kafejo tell us?

The root is kaf- (from kafo, coffee). The suffix -ej- means place associated with / place for something.

So:

kafejo = place for coffee → café, coffeehouse.

Other common examples:

lernejo – from lern- (learn) → place for learning → school
preĝejo – from preĝ- (pray) → place for prayer → church
banejo – from ban- (bathe) → place for bathing → bathroom / bathhouse

So whenever you see -ejo, think “the place where X normally happens or exists.”

What exactly does apud mean, and how is it different from ĉe or proksime de?

Apud means next to / beside / by, usually with the idea of very close, side-by-side.

In the sentence, en kafejo apud la muzeo suggests the café is right by the museum, not far away.

Comparison:

apud – beside, adjacent to
- apud la muzeo – next to the museum
ĉe – at, at the place of, by (location at or around something, not necessarily right beside it)
- ĉe la muzeo – at the museum (could be inside or just at its premises/entrance)
proksime de – near (but not necessarily adjacent)
- proksime de la muzeo – near the museum, somewhere in that area

So apud la muzeo emphasizes closeness: the café is right next to the museum.

Is the word order fixed? Could we say Vespere la koncerto komenciĝas, or move the other parts around?

Word order in Esperanto is fairly flexible, as long as it stays clear. The standard, neutral order is Subject – Verb – (Objects) – Other modifiers, but moving time and place phrases for emphasis is common.

All of these are possible and correct:

La koncerto komenciĝas vespere, sed ni jam sidas en kafejo apud la muzeo. (neutral)
Vespere la koncerto komenciĝas, sed ni jam sidas en kafejo apud la muzeo. (emphasis on “in the evening”)
La koncerto komenciĝas vespere, sed en kafejo apud la muzeo ni jam sidas. (stronger focus on where you already are)

Just avoid reordering in a way that makes it ambiguous what modifies what. But in this sentence, moving vespere or the en kafejo apud la muzeo chunk for emphasis is perfectly fine.

Why is there a comma before sed? Is that required in Esperanto?

The comma before sed separates two independent clauses:

La koncerto komenciĝas vespere
ni jam sidas en kafejo apud la muzeo

In modern Esperanto style, it is normal and recommended to put a comma before coordinating conjunctions (sed, kaj, aŭ) when they connect two full clauses, much like in careful English writing.

So:

La koncerto komenciĝas vespere, sed ni jam sidas… – preferred.

It isn’t absolutely “mathematically required” by some strict rulebook, but it’s good, standard style and helps readability.