Căpitanul pleacă azi.

Because -ul is the definite article for a masculine singular noun here.
So:

• căpitan = captain
• căpitanul = the captain

Romanian usually adds the to the end of the noun instead of putting it in front as English does.

Romanian normally uses a postposed definite article, which means the article comes after the noun, attached to it.

So instead of:

• English: the captain

Romanian says:

• căpitanul

This is one of the big differences between English and Romanian noun structure.

Pleacă is the 3rd person singular present tense of the verb a pleca.

• a pleca = to leave / to depart / to go away
• el/ea pleacă = he/she leaves

Since căpitanul is he/she/it grammatically, pleacă is the correct verb form.

Romanian, like English, often uses the present tense for a planned, expected, or near-future action, especially when a time word makes it clear.

Here, azi tells you the time, so pleacă azi can mean something like:

• leaves today
• is leaving today

This is very natural Romanian.

Because Romanian often drops subject pronouns when they are not needed.

The subject is already clear because:

1. căpitanul is explicitly named, and
2. the verb form pleacă matches a 3rd person singular subject.

So adding el would usually be unnecessary unless you want emphasis.

Yes. Romanian word order is fairly flexible, although Căpitanul pleacă azi is a very normal, neutral order.

You could also say:

• Căpitanul azi pleacă — possible, but less neutral
• Azi pleacă căpitanul — emphasizes today
• Pleacă azi căpitanul — can sound more marked or context-dependent

The original sentence is a simple, natural default pattern.

A rough guide:

• Căpitanul ≈ kuh-pee-TAH-nul
• pleacă ≈ PLEA-kuh
• azi ≈ AH-zee

A few useful sound notes:

• ă is a short central vowel, somewhat like the a in about
• că is not like English ka; it is softer and more neutral
• ea in pleacă is pronounced together as a diphthong

The main stresses are:

• căpiTAnul
• PLEAcă
• Azi

Yes, both mean today.

• azi = today
• astăzi = today

Azi is shorter and very common in everyday speech.
Astăzi can sound a little fuller, sometimes slightly more formal or emphatic, depending on context.

It can have a few closely related meanings depending on context:

• leaves
• is leaving
• departs
• goes away

So a pleca is broader than just physically walking out. It can be used for departing in general.

Here căpitanul is the subject of the sentence: it is the person doing the action.

So the structure is:

• căpitanul = subject
• pleacă = verb
• azi = time adverb

In other words, it follows a straightforward subject + verb + time expression pattern.