Το κάστρο είναι πολύ παλιό.

Το is the definite article, meaning the.

Greek articles change depending on the gender, number, and case of the noun.
Here, κάστρο is a neuter singular noun, so the correct article is το.

So:

• το κάστρο = the castle

Κάστρο is neuter.

One clue is its ending: many Greek neuter nouns in the singular end in -ο or -ι, though you should not rely on endings alone in every case.

Here are the forms of the castle in the singular:

• το κάστρο = nominative / accusative
• του κάστρου = genitive

So in this sentence, κάστρο is neuter singular nominative because it is the subject.

Είναι means is or it is / he is / she is, depending on context.

In this sentence, it links the subject το κάστρο with the description πολύ παλιό, just like English is in The castle is very old.

Greek often uses είναι in exactly this kind of sentence.
However, in some informal contexts, especially in headlines, signs, or short descriptions, Greek may sometimes leave it out. But in a normal full sentence like this, είναι is standard.

Because Greek often does not need subject pronouns when the verb already shows the person and number.

Here, είναι can mean:

• is
• he/she/it is

Since το κάστρο is already named, there is no need to add a separate pronoun.

Greek is a pro-drop language, meaning subject pronouns are often omitted unless needed for emphasis or clarity.

Here, πολύ is an adverb, meaning very.

It modifies the adjective παλιό:

• παλιό = old
• πολύ παλιό = very old

Be aware that πολύ can also sometimes behave like an adjective or pronoun in other contexts, but in this sentence it is simply an adverb.

Because the adjective has to agree with the noun it describes.

Since κάστρο is neuter singular, the adjective must also be neuter singular:

• παλιός = masculine singular
• παλιά = feminine singular
• παλιό = neuter singular

So:

• ο πύργος είναι πολύ παλιός = the tower is very old
• η πόλη είναι πολύ παλιά = the city is very old
• το κάστρο είναι πολύ παλιό = the castle is very old

In this sentence, παλιό comes after είναι because it is being used as a predicate adjective.

Structure:

• το κάστρο = subject
• είναι = is
• πολύ παλιό = predicate adjective phrase

This is normal in Greek, just as in English:
The castle is very old.

If the adjective comes directly before or after the noun, it works attributively instead:

• το παλιό κάστρο = the old castle

So compare:

• το κάστρο είναι παλιό = the castle is old
• το παλιό κάστρο = the old castle

Yes, Greek word order is often more flexible than English word order.

The most neutral order here is:

• Το κάστρο είναι πολύ παλιό.

But you may also hear variations for emphasis, such as:

• Πολύ παλιό είναι το κάστρο.
• Παλιό είναι το κάστρο.

These are not the most basic word orders for a beginner, but they are possible.

For learning purposes, it is best to stick with:

• subject + είναι + description

A natural pronunciation is approximately:

to KAS-tro EE-ne po-LEE pa-LYO

A more careful breakdown:

• Το = to
• κάστρο = KAS-tro
• είναι = EE-ne or EE-nai depending on style and speed
• πολύ = po-LEE
• παλιό = pa-LYO

A few notes:

• κ sounds like k
• στρ in κάστρο may feel tricky at first; practice KAS-tro
• λιό in παλιό sounds like lyo

The accent marks show which syllable is stressed.

In this sentence:

• κάστρο → stress on κά
• πολύ → stress on λύ
• παλιό → stress on the final ό

This matters because stress is important in Greek pronunciation and can sometimes distinguish words or forms.

Notice that το has no accent because it is unstressed here.

Greek spelling keeps the written accent according to standard rules, even if in connected speech some words are pronounced less strongly.

So είναι is written with an accent on εί, and learners should memorize it that way.

In natural speech, function words and common verbs may sound lighter than content words, but the written accent is still important and correct.

Usually yes in a sentence like this, but like most adjectives, its full range depends on context.

With buildings or objects, παλιό commonly means:

• old
• ancient
• not new

So for a castle, πολύ παλιό could suggest very old, quite old, or even ancient, depending on context.

Greek often uses παλιός / παλιά / παλιό for both age and older/long-standing things, just as English uses old in many ways.

Not in normal standard Greek.

The natural order is:

• πολύ παλιό = very old

So:

• Το κάστρο είναι πολύ παλιό. ✅

Putting πολύ after the adjective here sounds wrong or very unnatural for a basic statement.

As a beginner, treat πολύ + adjective as a fixed pattern:

• πολύ μεγάλο = very big
• πολύ όμορφο = very beautiful
• πολύ παλιό = very old

You would make both the noun and the adjective plural:

• Τα κάστρα είναι πολύ παλιά. = The castles are very old.

Changes:

• το → τα for neuter plural
• κάστρο → κάστρα
• παλιό → παλιά

Notice that είναι stays the same.

A very useful beginner pattern is:

article + noun + είναι + adverb + adjective

Using this sentence:

• Το = the
• κάστρο = castle
• είναι = is
• πολύ = very
• παλιό = old

You can build many similar sentences:

• Το σπίτι είναι πολύ μεγάλο. = The house is very big.
• Το βιβλίο είναι πολύ καλό. = The book is very good.
• Η πόλη είναι πολύ όμορφη. = The city is very beautiful.

This is a great model sentence for beginners.