Κάθομαι δίπλα σε έναν φίλο μου στο σινεμά.

Κάθομαι can mean both, depending on context:

• I sit
• I am sitting

In Greek, the present tense often covers both a general present and a current ongoing action.

So Κάθομαι δίπλα σε έναν φίλο μου στο σινεμά can mean:

• I sit next to a friend of mine at the cinema
• I am sitting next to a friend of mine at the cinema

Also, κάθομαι is the normal verb for to sit / be seated.

It looks passive, because -μαι is a typical mediopassive ending in Greek, but κάθομαι is a very common verb that simply means I sit / I am sitting.

So even though its form looks passive, you should learn it as a normal dictionary verb:

• κάθομαι = I sit / I am sitting

This is not unusual in Greek. Some verbs use mediopassive endings but have an active meaning in English.

δίπλα σε means next to / beside.

It works as a fixed expression:

• δίπλα = beside / alongside
• σε = to / at / in / on, depending on context

Together:

• δίπλα σε κάποιον / κάτι = next to someone / something

Examples:

• δίπλα σε μένα = next to me
• δίπλα στο σπίτι = next to the house
• δίπλα σε έναν φίλο = next to a friend

So you usually learn δίπλα σε as a unit.

Because after σε, the noun phrase goes in the accusative case.

Here:

• ένας φίλος = a friend → nominative
• έναν φίλο = a friend → accusative

Since the sentence has δίπλα σε, you need the accusative:

• δίπλα σε έναν φίλο

So:

• ένας φίλος = a friend
• βλέπω έναν φίλο = I see a friend
• δίπλα σε έναν φίλο = next to a friend

έναν is the masculine accusative singular form of ένας.

It can mean:

• a / an
• one, depending on emphasis

Here, it is most naturally understood as:

• a friend of mine

So:

• ένας φίλος = a friend
• έναν φίλο = a friend (accusative)

If you stressed it strongly, it could sound like one friend, but in this sentence it is just the normal indefinite article.

In Greek, possessive pronouns like μου often come after the noun:

• ο φίλος μου = my friend
• ένα βιβλίο μου = a book of mine
• έναν φίλο μου = a friend of mine

So φίλο μου literally looks like friend my, but that is normal Greek word order.

This is a very important distinction:

• έναν φίλο μου = a friend of mine
• τον φίλο μου = my friend

So in your sentence, έναν φίλο μου does not mean a specific friend already identified as my friend in the definite sense. It means one of my friends / a friend of mine.

Compare:

• Μιλάω με έναν φίλο μου. = I’m talking with a friend of mine.
• Μιλάω με τον φίλο μου. = I’m talking with my friend / my boyfriend, depending on context.

Yes, έναν φίλο would simply mean a friend.

Adding μου makes it:

• έναν φίλο μου = a friend of mine

So μου shows possession or personal connection:

• φίλος = friend
• φίλος μου = my friend
• ένας φίλος μου = a friend of mine

στο is a contraction of:

• σε + το = στο

This is extremely common in Greek.

So:

• στο σινεμά = at the cinema / in the cinema

Other examples:

• σε + τον = στον
• σε + τη(ν) = στη(ν)
• σε + το = στο
• σε + τους = στους

So στο is really σε το, just written in its normal contracted form.

Yes. σινεμά is neuter, so it takes the neuter article το.

That is why:

• το σινεμά = the cinema
• στο σινεμά = at/in the cinema

Also, σινεμά is one of those Greek nouns that often does not change much across cases in everyday language, so the form stays σινεμά.

It can mean either, depending on context.

Greek often uses σε for meanings that English splits into several prepositions:

• in
• at
• to
• on

So στο σινεμά may be translated as:

• at the cinema
• in the cinema

In this sentence, English would probably most naturally say:

• at the cinema or
• in the movie theater

Greek word order is more flexible than English, because case endings help show grammatical relationships.

So the sentence could be rearranged for emphasis, for example:

• Στο σινεμά κάθομαι δίπλα σε έναν φίλο μου.
• Δίπλα σε έναν φίλο μου κάθομαι στο σινεμά.

But the original order is very natural and neutral:

• Κάθομαι δίπλα σε έναν φίλο μου στο σινεμά.

A learner should usually stick to the original order until they become more comfortable with emphasis and style.

Not exactly.

• δίπλα σε έναν φίλο μου = next to a friend of mine
• με έναν φίλο μου = with a friend of mine

So:

• με means with
• δίπλα σε means next to / beside

You can be with someone without sitting next to them, so the meanings are related but not identical.

A rough pronunciation guide:

• Κάθομαι ≈ KA-tho-me
• δίπλα ≈ THEE-pla
• σε ≈ seh
• έναν ≈ EH-nan
• φίλο ≈ FEE-lo
• μου ≈ moo
• στο ≈ sto
• σινεμά ≈ see-ne-MA

A rough full pronunciation:

• KA-tho-me THEE-pla seh EH-nan FEE-lo moo sto see-ne-MA

A couple of useful sound notes:

• δ sounds like th in this
• θ sounds like th in think
• stress matters a lot in Greek, so notice:
  • Κάθομαι
  • δίπλα
  • έναν
  • φίλο
  • σινεμά

Yes, it is completely natural.

It sounds like normal spoken Greek and uses very common structures:

• κάθομαι = I sit / I’m sitting
• δίπλα σε = next to
• έναν φίλο μου = a friend of mine
• στο σινεμά = at the cinema

So it is a good sentence to learn from because it contains several very useful everyday patterns.