Η μουσική είναι πολύ έντονη απόψε, και δεν μπορώ να κοιμηθώ.

Η is the feminine singular definite article, so here it means the.
So η μουσική = the music.

Greek often uses the definite article more naturally than English does. In this sentence, it refers to the music that is currently playing.

Yes. Μουσική is grammatically feminine.

That is why it appears with:

• η for the
• έντονη in the feminine form

In Greek, articles and adjectives usually agree with the noun in gender, number, and case.

Because έντονη has to agree with μουσική, which is feminine singular nominative.

The adjective έντονος changes form:

• masculine: έντονος
• feminine: έντονη
• neuter: έντονο

So:

• η μουσική είναι έντονη
• not η μουσική είναι έντονος

Literally, έντονη means something like intense, strong, or powerful.

In this context, it suggests that the music feels overwhelming or forceful, so the natural English meaning may be too loud or very intense.

A more direct word for loud would often be δυνατή:

• Η μουσική είναι πολύ δυνατή = The music is very loud

So έντονη is understandable here, but it has a slightly different nuance from plain loud.

Πολύ means very here, and it modifies the adjective έντονη.

So:

• πολύ έντονη = very intense

The same word πολύ can also mean much or a lot, depending on the sentence.

Απόψε means tonight or this evening/tonight.

It is an adverb of time. It refers specifically to the current evening or night.

A longer way to say something similar would be:

• σήμερα το βράδυ = tonight / this evening

But απόψε is shorter and very common.

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

You could also say:

• Απόψε η μουσική είναι πολύ έντονη.
• Η μουσική απόψε είναι πολύ έντονη.

These all mean roughly the same thing, but the emphasis changes slightly.
Placing απόψε earlier can make tonight feel more prominent.

Because δεν is the normal negation used with finite verbs in statements.

So:

• μπορώ = I can
• δεν μπορώ = I can’t

In Greek, δεν usually comes directly before the verb it negates.

Μπορώ is the 1st person singular present tense of μπορώ.

It means:

• I can
• I am able to

So:

• μπορώ = I can
• δεν μπορώ = I can’t

Modern Greek generally does not use an infinitive the way English does.

Instead, it usually uses:

• να
  • a verb form

So after μπορώ, Greek says:

• μπορώ να κοιμηθώ

This is the normal Greek structure for I can sleep / I can fall asleep.

This is a very common learner question.

Κοιμάμαι means I sleep / I am sleeping.
Κοιμηθώ is the aorist subjunctive form, used after να, and here it usually means to fall asleep or to get to sleep.

So:

• δεν μπορώ να κοιμηθώ = I can’t fall asleep / I can’t get to sleep

That is the natural Greek way to say I can’t sleep in a situation like this, where noise is stopping you from falling asleep.

If you used να κοιμάμαι, it would suggest more of an ongoing or repeated state, which is not what this sentence is focusing on.

Greek punctuation is a little more flexible here than English.

The comma before και can mark a pause between two related clauses:

• Η μουσική είναι πολύ έντονη απόψε
• δεν μπορώ να κοιμηθώ

You may also see this written without the comma. Both are possible, depending on style and rhythm.

A rough pronunciation guide is:

ee moo-see-KEE EE-ne po-LEE EN-to-nee a-PO-pse, ke then bo-RO na kee-mee-THO

A few useful pronunciation notes:

• η sounds like ee
• οι in μουσική and κοιμηθώ sounds like ee
• δ in δεν sounds like the th in this
• θ in κοιμηθώ sounds like the th in think
• ψ in απόψε sounds like ps

The main stresses are:

• μουσική
• είναι
• πολύ
• έντονη
• απόψε
• μπορώ
• κοιμηθώ