Το φεγγάρι είναι ψηλά πάνω από το βουνό.

Because το is the neuter singular definite article in Greek, meaning the.

• το φεγγάρι = the moon
• το βουνό = the mountain

Greek uses articles very regularly, often more regularly than English. Since both φεγγάρι and βουνό are neuter singular nouns, they both take το.

είναι means is. It is the 3rd person singular form of the verb to be.

So:

• Το φεγγάρι είναι... = The moon is...

You will see είναι used constantly in Greek:

• Είναι μεγάλο. = It is big.
• Είναι εδώ. = It is here.

In this sentence, ψηλά functions like an adverb, meaning high or high up, not like an adjective describing a noun directly.

So:

• Το φεγγάρι είναι ψηλά = The moon is high / high up

This is different from using an adjective before a noun, such as:

• το ψηλό βουνό = the tall mountain

Here, ψηλό is an adjective agreeing with βουνό. But ψηλά in your sentence describes where the moon is, so it works adverbially.

Yes, they are related, but they do slightly different jobs.

• ψηλά = high / high up
• πάνω από το βουνό = above the mountain / over the mountain

Together they give a fuller picture:

• Το φεγγάρι είναι ψηλά πάνω από το βουνό.
• The moon is high above the mountain.

If you remove one part, the sentence still works, but the meaning changes slightly:

• Το φεγγάρι είναι πάνω από το βουνό. = The moon is above the mountain.
• Το φεγγάρι είναι ψηλά. = The moon is high up.

So using both is natural and adds detail.

πάνω από means above, over, or higher than, depending on context.

In this sentence:

• πάνω από το βουνό = above the mountain

A very important distinction:

• πάνω από usually means above / over, not touching
• πάνω σε or πάνω στο usually means on, in contact with something

For example:

• Το πουλί είναι πάνω από το σπίτι. = The bird is above the house.
• Το βιβλίο είναι πάνω στο τραπέζι. = The book is on the table.

Yes. από takes the accusative case in Modern Greek.

So after από, you use the accusative form of the noun phrase:

• από το βουνό = from/than/above the mountain, depending on context

In this particular sentence, πάνω από works together as a prepositional phrase, and το βουνό is in the accusative, which is exactly what you expect after από.

The good news is that for many neuter nouns, the nominative and accusative singular look the same, so το βουνό does not change form.

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

The neutral, natural version is:

• Το φεγγάρι είναι ψηλά πάνω από το βουνό.

But Greek can move things around for emphasis, for example:

• Ψηλά πάνω από το βουνό είναι το φεγγάρι.
• Πάνω από το βουνό το φεγγάρι είναι ψηλά.

These may sound more poetic or emphatic depending on context. English is usually less flexible, but Greek often allows rearrangement because grammar is shown not only by position but also by articles and endings.

Yes, φεγγάρι is the common everyday word for moon.

You may also encounter σελήνη, which is a more formal, literary, or scientific word.

So:

• φεγγάρι = the usual everyday word
• σελήνη = more formal, poetic, or scientific

In ordinary speech, το φεγγάρι is exactly what most people would say.

A simple pronunciation guide is:

• Το φεγγάρι = to feg-GA-ri
• είναι = EE-ne
• ψηλά = psee-LA
• πάνω = PA-no
• από = a-PO
• το βουνό = to vou-NO

A few useful notes:

• γγ in φεγγάρι sounds like ng as in finger, followed by a hard g sound.
• ψ in ψηλά sounds like ps, as in the end of lapse.
• The accent mark shows which syllable is stressed.

In a normal sentence like this, είναι is usually kept.

So you normally say:

• Το φεγγάρι είναι ψηλά πάνω από το βουνό.

Dropping είναι would sound incomplete or unnatural in standard Modern Greek prose. Greek is not like Russian or Arabic, where the present-tense to be is often omitted in simple statements.

It can be used both literally and more broadly.

In your sentence, it is literal:

• The moon is high up

But ψηλά can also be used in other ways, for example:

• Μιλάει ψηλά. = He/She speaks loudly.
  (in some contexts or dialectal usage)
• Οι τιμές είναι ψηλά. = Prices are high.

So the core idea is high, but the exact meaning depends on context.

Yes. επάνω από and πάνω από are very close in meaning.

• πάνω από το βουνό
• επάνω από το βουνό

Both can mean above the mountain. In everyday speech, πάνω από is extremely common and natural. επάνω από may sound a bit fuller or slightly more formal in some contexts, but both are correct.

Because Greek often expresses that idea with είναι ψηλά or another location phrase rather than a special verb meaning to be up.

So:

• Το φεγγάρι είναι ψηλά. = The moon is high / up.
• Το φεγγάρι είναι πάνω από το βουνό. = The moon is above the mountain.

Greek typically builds this meaning through to be + adverb/prepositional phrase, which is very normal.