Le dernier train est déjà parti.

It is the passé composé, a very common French past tense.

Here it is built like this:

• est = the auxiliary verb
• parti = the past participle of partir

So est parti is the passé composé of partir for il / elle / on or any singular noun that takes être.

Because partir is one of the verbs that form the passé composé with être, not avoir.

So:

• il est parti = he left / he has left
• not il a parti

This happens with several verbs of movement or change of state, such as aller, venir, arriver, partir, entrer, sortir, tomber, naître, mourir.

Because the past participle agrees with the subject when the verb uses être.

The subject here is le dernier train, and train is:

• masculine
• singular

So the correct form is parti.

Compare:

• Le train est parti.
• La voiture est partie.
• Les trains sont partis.
• Les voitures sont parties.

In compound tenses like the passé composé, short adverbs such as déjà, bien, mal, beaucoup, trop, souvent often go between the auxiliary and the past participle.

So:

• est déjà parti = natural
• déjà est parti = wrong here
• est parti déjà = possible in some contexts, but much less natural

This placement is very common and worth memorizing.

Here dernier means last in the sense of final.

So le dernier train means the final train available, usually the last scheduled train of the evening or the last one that could be taken.

It does not mean the train at the back unless the context is very unusual.

Because that is the normal position here.

With dernier, word order can affect meaning:

• le dernier train = the last / final train
• la semaine dernière = last week

So in this sentence, dernier comes before the noun because it means final / last one in the series.

Le train dernier would not sound natural here.

Because French usually uses a definite article here: the last train = le dernier train.

It refers to a specific, identifiable train, not just any train.

Compare:

• Le dernier train est déjà parti. = The last train has already left.
• Un dernier train would mean something more like one last train or a final train, which is a different idea.

Yes.

French passé composé often corresponds to either:

• the English simple past: left
• or the English present perfect: has left

So depending on context, this sentence could be understood as:

• The last train left already
• The last train has already left

In natural English, has already left is usually the best match here.

Grammatically, it is a past participle used as part of the verb phrase est parti.

So the structure is verbal: it is the passé composé of partir.

That said, with verbs that use être, French can sometimes feel a little close to an adjective in English, especially in translation:

• Il est parti. = He has left. / He is gone.

But in this sentence, parti is primarily functioning as part of the tense, not just as an ordinary adjective.

A careful pronunciation is approximately:

Le dernier train est déjà parti
/lə dɛʁnje tʁɛ̃ ɛ deʒa paʁti/

A few useful points:

• le sounds like luh
• dernier ends with a -yé sound
• train has a nasal vowel; the final n is not pronounced as a normal n
• est is pronounced eh
• the final t in est is silent
• déjà sounds like day-zha
• parti ends with a clear tee

There is no liaison between est and déjà because déjà begins with a consonant sound.