Η επίδειξη αρχίζει στις οκτώ.

A natural pronunciation is:

ee eh-PEE-theek-see ar-HEE-zee stees ok-TOH

A more careful transliteration would be:

i epídeixi archízei stis októ

A few pronunciation notes:

• Η is pronounced ee.
• ει in επίδειξη sounds like ee.
• ξ sounds like ks.
• χ in αρχίζει is not like English ch. It is a throaty sound, like the ch in German Bach or Scottish loch.
• The stressed syllables are marked by the accents:
  • επίδειξη
  • αρχίζει
  • οκτώ

Η is the definite article here, meaning the.

So:

• η επίδειξη = the show / the demonstration / the display

Greek articles change for gender, number, and case. Here:

• η = feminine singular nominative

That tells you that επίδειξη is a feminine singular noun and that it is the subject of the sentence.

Yes, επίδειξη is feminine.

You can tell partly from the article:

• η επίδειξη

In Greek, the article usually makes the gender very clear. The ending -η often belongs to feminine nouns, though you should not rely on endings alone in every case.

So in this sentence:

• η επίδειξη = feminine singular subject

Επίδειξη can mean several related things depending on context, such as:

• demonstration
• display
• show
• presentation

In a sentence like this, it often means something like:

• the show starts at eight
• the demonstration begins at eight

The exact English translation depends on context. For example, it could be a product demonstration, a fashion show, or some other kind of presentation.

Αρχίζει is the verb begin / start in the:

• present tense
• third person singular

So literally it means:

• it begins
• it starts

Because the subject is η επίδειξη (the show), the full sense is:

• the show begins
• the show starts

The basic dictionary form is αρχίζω = I begin / I start.

A few useful forms:

• αρχίζω = I begin
• αρχίζεις = you begin
• αρχίζει = he/she/it begins

In Greek, clock times are commonly introduced with στις.

So:

• στις οκτώ = at eight
• στις τρεις = at three
• στις έξι = at six

This is the normal way to say at + hour.

So the structure is:

• αρχίζει στις οκτώ = it starts at eight

Στις is a contraction of:

• σε + τις → στις

Historically and grammatically, this is why it looks the way it does.

For learners, the important thing is simply to recognize:

• στις = at when talking about a specific hour

You do not usually need to unpack it every time, but it helps explain why the form is not just σε.

This confuses many learners.

Greek uses στις with hours because the expression is understood as something like:

• στις οκτώ ώρες = at eight hours

Even though ώρες is not actually spoken, the plural article remains in the time expression.

So you normally say:

• στις οκτώ = at eight o’clock

A very common exception is one o’clock:

• στη μία = at one

That is singular because μία is singular.

Compare:

• στη μία = at one
• στις δύο = at two
• στις οκτώ = at eight

No. Οκτώ stays the same.

Greek numerals like οκτώ are generally not inflected in this kind of everyday time expression. So you just learn:

• στις οκτώ = at eight

The important grammar is mostly carried by στις, not by a changed form of οκτώ.

Yes, Greek word order is more flexible than English, though the most neutral order here is:

• Η επίδειξη αρχίζει στις οκτώ.

You might also hear:

• Στις οκτώ αρχίζει η επίδειξη.

This version emphasizes the time a bit more, something like:

• At eight, the show begins.

Both are correct. The original sentence is just the most straightforward, neutral way to say it.

Normally, no, not in standard everyday Greek for this meaning.

Greek uses the definite article more often than English does. So:

• Η επίδειξη αρχίζει στις οκτώ = normal
• Επίδειξη αρχίζει στις οκτώ = sounds incomplete or unusual in most contexts

You might see article omission in headlines, notes, labels, or very special styles, but for ordinary speech and writing, the article is expected.

No. A very common alternative is:

• Η επίδειξη ξεκινά στις οκτώ.
• Η επίδειξη ξεκινάει στις οκτώ.

These also mean:

• The show starts at eight.

Very roughly:

• αρχίζει = begins / starts
• ξεκινά(ει) = starts / sets off / begins

In many everyday situations, they are interchangeable.

The accent marks show which syllable is stressed.

In this sentence:

• επίδειξη? Actually the stress is on δεί: ε-πεί-δει-ξη?
  More clearly written by syllables: ε-πί-δει-ξη is not correct. The correct stress is on δεί? No—the written accent is on ί, so the stress is on πί: ε-πί-δει-ξη.
• αρχίζει
• οκτώ

So the stressed syllables are:

• ε-πί-δει-ξη
• αρ-χί-ζει
• οκ-τώ

Stress matters in Greek and is always written in normal spelling for words of more than one syllable.

Greek often uses the present tense for scheduled or fixed future events, just as English can.

Compare English:

• The show starts at eight tomorrow.

That is present tense in form, but future in meaning.

Greek works similarly:

• Η επίδειξη αρχίζει στις οκτώ.

Depending on context, this can mean:

• The show starts at eight
• The show is starting at eight
• The show begins at eight

If the event is scheduled, the present tense is very natural.