La reunión ya ha empezado.

In Spain, this is very common when talking about something that happened recently or within a time period that still feels connected to the present.

• La reunión ya ha empezado = the meeting has already started
• La reunión ya empezó = the meeting already started

In many parts of Latin America, the simple past empezó is often used where speakers in Spain would prefer ha empezado.

So for Spanish from Spain, ya ha empezado sounds very natural.

It is the present perfect.

It is made with:

• haber in the present: ha
• the past participle: empezado

So:

• ha = has
• empezado = started

Together, ha empezado means has started.

Because Spanish forms the present perfect with the auxiliary verb haber, not with ser or estar.

So:

• he empezado = I have started
• has empezado = you have started
• ha empezado = he/she/it has started

English uses have/has. Spanish uses forms of haber.

Ya here means already.

So:

• La reunión ha empezado = the meeting has started
• La reunión ya ha empezado = the meeting has already started

It adds the idea that the action happened sooner than expected, or that by now it is already true.

In Spanish, ya usually goes before the verb phrase it modifies.

So La reunión ya ha empezado is the normal word order.

You may also hear other orders in special contexts, but this is the standard and most natural one for learners.

Spanish uses definite articles much more often than English.

So even where English says the meeting, Spanish naturally says la reunión.

Leaving out the article would usually sound incomplete here.
La reunión is the full noun phrase and acts as the subject of the sentence.

Yes, reunión is a feminine noun, which is why it takes la.

You learn this from usage: la reunión.

A lot of nouns ending in -ión are feminine:

• la reunión
• la conversación
• la decisión

So this ending is a useful clue, though you should still learn nouns with their article.

Because empezar is an -ar verb, and the past participle of regular -ar verbs ends in -ado.

Examples:

• hablar → hablado
• llegar → llegado
• empezar → empezado

So ha empezado literally follows the regular pattern.

Yes. That sentence is also correct.

The difference is mainly one of usage and regional preference:

• In Spain, La reunión ya ha empezado is very common for a recent event with present relevance.
• In much of Latin America, La reunión ya empezó is often more common in the same situation.

If you are learning Spanish from Spain, the version with ha empezado is especially useful.

Yes.

• La reunión ya ha empezado
• La reunión ya ha comenzado

Both mean the same thing: the meeting has already started.

Empezar is often a bit more common in everyday speech, while comenzar can sound slightly more formal in some contexts, but both are standard.

The accent mark shows the stressed syllable: reu-NIÓN.

Without the accent mark, Spanish stress rules would suggest a different pronunciation. The written accent tells you that the stress falls on the last syllable.

So you pronounce it roughly as:

• reh-oo-NYON

The final -ión is a very common stressed ending in Spanish nouns.

A natural pronunciation would be roughly:

• ya a em-pe-THA-do in much of Spain
• ya a em-pe-SA-do in areas without the th sound

A few notes:

• ya sounds like yah
• ha has a silent h
• empezado has stress on -za-

In connected speech, ya ha often flows together very smoothly, almost like one unit.

Yes.

• La reunión ha empezado = the meeting has started
• La reunión ya ha empezado = the meeting has already started

Without ya, the sentence is more neutral.
With ya, it emphasizes that the meeting is already underway.

The subject is La reunión.

That is the thing performing the action of starting.

So the structure is:

• La reunión = subject
• ya = adverb
• ha empezado = verb phrase

Even though in English we often think of people starting meetings, in Spanish the meeting itself can naturally be the subject: the meeting has started.