Η καθυστέρηση απόπλου είναι μεγάλη.

A word-by-word breakdown is:

• Η = the (feminine singular nominative article)
• καθυστέρηση = delay
• απόπλου = of departure / of sailing / departure
  Here it specifies what kind of delay it is: a departure delay
• είναι = is
• μεγάλη = big / great / long / significant (feminine singular)

So the structure is basically:

The delay of departure is great
or more naturally in English: The departure delay is long/significant.

Η is the feminine singular form of the.

It is used because καθυστέρηση is:

• feminine
• singular
• the subject of the sentence

Greek articles change according to gender, number, and case, so you do not always use the same form as in English.

Here:

• η καθυστέρηση = the delay

Because it agrees with καθυστέρηση, which is a feminine singular noun.

In Greek, adjectives must agree with the noun they describe in:

• gender
• number
• case

So:

• masculine: μεγάλος
• feminine: μεγάλη
• neuter: μεγάλο

Since καθυστέρηση is feminine singular, the adjective must be μεγάλη.

For the same reason: the adjective after είναι still agrees with the subject.

In English, we say the delay is big without changing big.
In Greek, the adjective changes form:

• Η καθυστέρηση είναι μεγάλη = The delay is big/long/significant
• Το πρόβλημα είναι μεγάλο = The problem is big
• Ο θόρυβος είναι μεγάλος = The noise is loud/great

So even after είναι, Greek adjectives still match the noun.

απόπλου is in the genitive singular.

It comes from the noun ο απόπλους (departure by ship, sailing, setting sail).
Its genitive is απόπλου.

The genitive is used here to show a relationship like:

• delay of departure
• departure delay

So:

• καθυστέρηση απόπλου = delay of departure

This is very common in Greek, especially in formal or technical language.

Greek often leaves out the article in this kind of formal noun + genitive expression.

So καθυστέρηση απόπλου sounds like:

• departure delay
• delay of departure

If you added the article, καθυστέρηση του απόπλου, it would sound more specifically like:

• the delay of the departure
• referring to a particular departure already known in context

So the version without the article is more general, compact, and typical of announcements, notices, or formal wording.

Not especially in casual everyday speech. It is more common in:

• travel language
• shipping/ferry language
• announcements
• official or formal contexts

A learner is more likely to meet it in signs, schedules, or transportation notices than in relaxed conversation.

That means the whole sentence sounds somewhat formal or announcement-like.

Yes, Greek can place adjectives before or after the noun, but the meaning or emphasis can shift slightly.

• Η καθυστέρηση απόπλου είναι μεγάλη = The departure delay is large/significant
• Η μεγάλη καθυστέρηση απόπλου = the big/serious departure delay

In your sentence, μεγάλη comes after είναι because it is part of the predicate:

• is large
• is significant

So this is the normal structure for X is Y.

You could translate it literally that way, but it may sound unnatural in English.

More natural English translations would be:

• The departure delay is significant.
• There is a long delay in departure.
• The departure has been seriously delayed.
• The delay in departure is long.

The best English version depends on context, especially whether this is about a ship, ferry, or another official transport announcement.

Greek often uses μεγάλος / μεγάλη / μεγάλο in situations where English may prefer:

• big
• great
• long
• serious
• significant

So μεγάλη καθυστέρηση does not always mean physically big.
It can mean:

• a long delay
• a major delay
• a significant delay

This is very natural in Greek.

Yes. καθυστέρηση is in the nominative singular because it is the subject of the sentence.

You can identify it as the subject because:

• it is the thing being described
• the sentence says something about it: it is μεγάλη

So:

• Η καθυστέρηση = subject
• είναι μεγάλη = what is being said about the subject

A helpful pronunciation guide is:

i kathistérisi apóplou íne megáli

A few notes:

• Η sounds like ee
• θ sounds like th in think
• η / ι / ει / οι / υ all sound like ee in Modern Greek
• stress matters:
  • καθυστέρηση
  • απόπλου
  • είναι
  • μεγάλη

The standard order here is very natural:

Η καθυστέρηση απόπλου είναι μεγάλη.

Greek word order is more flexible than English because endings show grammatical roles. So other orders are possible for emphasis, for example:

• Μεγάλη είναι η καθυστέρηση απόπλου.
  = The departure delay is significant.
• Η καθυστέρηση είναι μεγάλη.
  = The delay is large/long.

But the original sentence is the most straightforward neutral version.

Yes. That would mean:

There is a big/significant departure delay.

This is also very natural Greek, especially in announcements.

Compare:

• Η καθυστέρηση απόπλου είναι μεγάλη.
  = The departure delay is significant.
• Υπάρχει μεγάλη καθυστέρηση απόπλου.
  = There is a significant departure delay.

Both are correct; the second one may sound slightly more like an announcement or report of a situation.