Η ακτοπλοϊκή εταιρεία αλλάζει το ακτοπλοϊκό εισιτήριο.

Because the adjective has to agree with the noun it describes in gender, number, and case.

• η ακτοπλοϊκή εταιρεία
  
  • εταιρεία is feminine singular, so the adjective is ακτοπλοϊκή.
• το ακτοπλοϊκό εισιτήριο
  
  • εισιτήριο is neuter singular, so the adjective is ακτοπλοϊκό.

This is very normal in Greek: adjectives change form depending on the noun.

They are the definite articles, equivalent to the in English.

• η = the for a feminine singular noun
• το = the for a neuter singular noun

So:

• η εταιρεία = the company
• το εισιτήριο = the ticket

Unlike English, Greek articles change depending on gender, number, and case.

In Greek, every noun has a grammatical gender: masculine, feminine, or neuter.

εταιρεία happens to be a feminine noun. This is a grammatical feature, not necessarily a statement about biological sex. Many nouns referring to things or abstract concepts are feminine.

You just learn nouns together with their article:

• η εταιρεία
• το εισιτήριο
• ο άνθρωπος

That helps you remember their gender.

αλλάζει is the 3rd person singular present tense form of the verb αλλάζω (to change).

So it means:

• he/she/it changes
• is changing

In this sentence, the subject is η ακτοπλοϊκή εταιρεία, which is singular, so the verb is also singular:

• η εταιρεία αλλάζει = the company changes / is changing

It can mean either, depending on context.

Greek present tense often covers both:

• a general/habitual meaning: changes
• an ongoing meaning: is changing

So without extra context, αλλάζει could be understood as either:

• The ferry company changes the ferry ticket
• The ferry company is changing the ferry ticket

Usually the wider context makes it clear.

εισιτήριο is the direct object of the sentence, so it is in the accusative case. But with many neuter singular nouns, the nominative and accusative forms are the same.

So:

• nominative: το εισιτήριο
• accusative: το εισιτήριο

They look identical.

You can tell it is the object because of its role in the sentence: it is the thing being changed.

Because in Greek, adjectives commonly come before the noun, especially in neutral, everyday descriptions.

So:

• ακτοπλοϊκή εταιρεία = ferry/shipping company
• ακτοπλοϊκό εισιτήριο = ferry ticket

Greek adjectives can sometimes come after the noun too, but the position before the noun is very common and natural here.

Yes, Greek word order is more flexible than English because case endings and articles help show grammatical relationships.

The neutral, straightforward order here is:

• Η ακτοπλοϊκή εταιρεία αλλάζει το ακτοπλοϊκό εισιτήριο.

But other orders are possible for emphasis, for example:

• Το ακτοπλοϊκό εισιτήριο αλλάζει η ακτοπλοϊκή εταιρεία.

That sounds more marked, with emphasis on the ticket.

So yes, the order can change, but the original sentence is the most natural default order.

Greek does have an indefinite article (ένας, μία/μια, ένα) for a/an, but this sentence uses the definite article because it says the company and the ticket.

So:

• η εταιρεία = the company
• μια εταιρεία = a company

and

• το εισιτήριο = the ticket
• ένα εισιτήριο = a ticket

The ending -ει here tells you this is a 3rd person singular present form.

From αλλάζω:

• εγώ αλλάζω = I change
• εσύ αλλάζεις = you change
• αυτός/αυτή/αυτό αλλάζει = he/she/it changes

So when you see αλλάζει, you should think he/she/it changes or is changing.

Because each noun phrase is being described separately.

• ακτοπλοϊκή εταιρεία = a company related to ferry/coastal shipping
• ακτοπλοϊκό εισιτήριο = a ticket related to ferry/coastal shipping

English sometimes repeats adjectives too, and Greek does this very naturally. The adjective must be attached to each noun it describes.

Those dots are called diaeresis in English and διαλυτικά in Greek.

They show that the ι is pronounced separately, not merged into a vowel combination.

So -οϊ- is pronounced as two separate vowel sounds, not as one combined sound.

This helps with pronunciation and reading. Without the dots, a learner might try to read the vowels together.

In Modern Greek, several different spellings can represent the ee sound /i/.

In εταιρεία, the combinations ει and the letter ι both sound like ee.

So although the spelling looks complex, Modern Greek pronunciation is more regular than it first seems.

A rough pronunciation is:

• εταιρεία ≈ e-te-ree-a
  (more accurately, the stress is on -εί-: e-te-RI-a)

Greek spelling preserves older distinctions that are no longer pronounced differently in Modern Greek.

Grammatically, εταιρεία is feminine, so Greek uses feminine agreement with words that refer back to it.

But when translating into English, you would usually say it for a company:

• Η εταιρεία αλλάζει...
• It is changing...

So in Greek grammar it is feminine, but in normal English translation it is usually it, not she.

In some contexts, yes, but it would change the feel or meaning.

With articles:

• Η ακτοπλοϊκή εταιρεία αλλάζει το ακτοπλοϊκό εισιτήριο.
• The ferry company is changing the ferry ticket.

Without articles:

• Ακτοπλοϊκή εταιρεία αλλάζει ακτοπλοϊκό εισιτήριο.

That sounds less natural as an ordinary full sentence and more like a headline, label, or very compressed style.

In normal speech and writing, Greek often uses articles where English might sometimes omit them.

The dictionary forms are:

• η εταιρεία = company
• το εισιτήριο = ticket
• αλλάζω = to change
• ακτοπλοϊκός, -ή, -ό = ferry / coastal-shipping-related

For adjectives, dictionaries usually give the masculine, feminine, and neuter endings, such as:

• ακτοπλοϊκός, ακτοπλοϊκή, ακτοπλοϊκό

That helps you recognize the different agreement forms.