Ο κατάπλους του επιβατηγού πλοίου είναι σήμερα.

Κατάπλους is a fairly formal, nautical word meaning arrival in port, putting in, or coming into harbor.

So this sentence is not just saying that the ship arrives in a general sense, but more specifically that it comes into port.

A learner should also know that this is not an everyday casual word in most conversation. In ordinary speech, people would often use a simpler expression with a verb, such as Το επιβατηγό πλοίο φτάνει σήμερα (The passenger ship arrives today).

Ο is the definite article meaning the, and here it goes with κατάπλους.

• ο κατάπλους = the arrival in port

Even though πλοίου (ship) also appears in the sentence, the main noun of the sentence is κατάπλους, not πλοίο. That is why the article is attached to κατάπλους.

Because του πλοίου is in the genitive case, and it means of the ship.

The structure is:

• ο κατάπλους = the arrival in port
• του επιβατηγού πλοίου = of the passenger ship

So literally, the sentence is:

• The arrival in port of the passenger ship is today.

Greek often uses the genitive in places where English uses of.

Because επιβατηγού is describing πλοίου, so it has to match it in case, number, and gender.

Here:

• πλοίου = genitive singular
• επιβατηγού = genitive singular, matching πλοίου

So:

• επιβατηγό πλοίο = passenger ship (nominative)
• του επιβατηγού πλοίου = of the passenger ship (genitive)

This agreement is very important in Greek adjectives.

Their basic dictionary forms are:

• πλοίο = ship
• επιβατηγός / επιβατηγό = passenger (used as an adjective, depending on gender)

In this sentence, they appear in the genitive because they are part of the phrase of the passenger ship.

So a learner should recognize that Greek words often change form depending on their role in the sentence.

Είναι means is.

The sentence is structured like:

• Ο κατάπλους του επιβατηγού πλοίου = the arrival in port of the passenger ship
• είναι σήμερα = is today

So Greek is linking the subject to σήμερα with είναι.

In English, we might more naturally say The passenger ship arrives today, but Greek here uses a noun phrase plus is:

• The arrival in port of the passenger ship is today.

That sounds formal in English, and it is also somewhat formal in Greek.

Greek word order is more flexible than English word order.

Placing σήμερα at the end is completely natural here. It gives the time information after the main statement:

• Ο κατάπλους του επιβατηγού πλοίου είναι σήμερα.

You could also hear other word orders depending on emphasis, such as:

• Σήμερα είναι ο κατάπλους του επιβατηγού πλοίου.

That would put more focus on today.

So the end position does not mean anything strange by itself; it is just a normal Greek ordering.

It is grammatical and natural, but it sounds formal, official, or written, especially because of κατάπλους.

You might see this kind of wording in:

• port announcements
• schedules
• official notices
• news reports

In everyday speech, many speakers would be more likely to say something simpler, for example:

• Το επιβατηγό πλοίο φτάνει σήμερα.
  The passenger ship arrives today.

Yes. Κατάπλους is a masculine noun:

• ο κατάπλους

Greek noun gender is not always obvious from the ending alone, so it is best to learn nouns together with their article:

• ο κατάπλους
• το πλοίο

That helps you remember both the gender and the correct article.

A very literal breakdown would be:

• Ο = the
• κατάπλους = arrival in port
• του = of the
• επιβατηγού = passenger
• πλοίου = ship
• είναι = is
• σήμερα = today

So, word for word:

• The arrival in port of the passenger ship is today.

That is useful for understanding the grammar, even if the most natural English translation would probably be:

• The passenger ship arrives today.

It is a genitive modifier attached to κατάπλους.

In other words, it answers the question:

• Whose / which arrival in port?
• The arrival in port of the passenger ship.

So the whole subject is not just ο κατάπλους, but:

• Ο κατάπλους του επιβατηγού πλοίου

This entire phrase acts as the subject of είναι.

Yes, very easily. Greek often has both options:

Noun-based, more formal:

• Ο κατάπλους του επιβατηγού πλοίου είναι σήμερα.

Verb-based, more everyday:

• Το επιβατηγό πλοίο καταπλέει σήμερα.
• Το επιβατηγό πλοίο φτάνει σήμερα.

The first version sounds more official or technical. The later versions sound more direct and conversational.