Στο σπίτι επικοινωνώ με τη φίλη μου μόνο στα ελληνικά όταν κάνουμε βιντεοκλήση.

Στο σπίτι literally means in/at the house, i.e. at home.

• στο = σε + το (preposition σε “in/at” + article το “the” for neuter singular)
• σπίτι = “house, home”

So:

• σε + το σπίτι → στο σπίτι

You can’t say just σε σπίτι here; in standard Greek, when you talk about a specific place like “at home”, you normally include the article and contract it:

• στο σπίτι = correct and natural
• σε το σπίτι = grammatical but never used; always contracted to στο σπίτι

Greek is a pro‑drop language: the subject pronoun is usually omitted because the verb ending shows who is doing the action.

• επικοινωνώ is 1st person singular: I communicate
• So (Εγώ) επικοινωνώ → Επικοινωνώ

Εγώ is only used when you want to emphasize I:

• Εγώ στο σπίτι επικοινωνώ… = I (as opposed to others) at home communicate…

επικοινωνώ means to communicate, to be in contact (with someone). It’s a bit more general and can sound slightly more formal or neutral than μιλάω.

• επικοινωνώ με τη φίλη μου = I communicate / keep in touch with my friend
• μιλάω με τη φίλη μου = I talk with my friend

In this sentence, επικοινωνώ fits well because a video call is a means of communication, not just speaking, and it can include chatting, seeing each other, etc. You could also say:

• Στο σπίτι μιλάω με τη φίλη μου μόνο στα ελληνικά όταν κάνουμε βιντεοκλήση.

That would be perfectly natural too, just a little more casual.

Several things are happening here:

1. Case after με
   The preposition με (“with”) takes the accusative case.

   • Nominative: η φίλη (the friend – subject)
   • Accusative: τη(ν) φίλη (the friend – object)
     After με, we need τη φίλη.

2. Article form: τη vs την
   The full form is την. In modern usage, the final ν is often dropped before many consonants, including φ:

   • την φίλη → τη φίλη

   Both spellings are technically acceptable; in everyday writing you’ll usually see τη φίλη.

3. Word order with possessive
   Possessive pronouns go after the noun in Greek:

   • η φίλη μου = my friend
     Not η μου φίλη.

So με τη φίλη μου = with my friend:

• με (with) + τη (the, accusative feminine) + φίλη (friend) + μου (my).

In Greek, weak possessive pronouns (my, your, his, etc.) normally come after the noun:

• η φίλη μου = my friend
• το σπίτι μου = my house
• η μαμά σου = your mom

You don’t say μου φίλη in standard Greek. If you want to emphasize possession strongly, you use the strong form δικός/δική/δικό:

• η δική μου φίλη = my friend (as opposed to someone else’s)

But the neutral, everyday way is: η φίλη μου.

μόνο means only. Here it limits στα ελληνικά:

• επικοινωνώ … μόνο στα ελληνικά = I communicate only in Greek.

You can move μόνο, but its exact position changes what is “only”:

• Στο σπίτι επικοινωνώ με τη φίλη μου μόνο στα ελληνικά…
  → The language is limited: only in Greek.

• Στο σπίτι επικοινωνώ μόνο με τη φίλη μου στα ελληνικά…
  → The person is limited: only with my friend (not with others) in Greek.

• Μόνο στο σπίτι επικοινωνώ με τη φίλη μου στα ελληνικά…
  → The place is limited: only at home I talk with her in Greek.

So placement of μόνο is important for the meaning.

When talking about languages, modern Greek usually uses the neuter plural with the article:

• τα ελληνικά = (the) Greek (language)
• στα ελληνικά = σε + τα ελληνικά → in Greek

So:

• μιλάω ελληνικά = I speak Greek (no article)
• μιλάω στα ελληνικά = I speak in Greek (with article)

Both forms are common; στα ελληνικά sounds a bit more explicit: in the Greek language.

στην ελληνική would usually need a noun after it (because ελληνική by itself is just the adjective “Greek” feminine):

• στην ελληνική γλώσσα = in the Greek language
  Without γλώσσα, στην ελληνική sounds incomplete here.

Grammatically, τα ελληνικά is neuter plural. Many language names in Greek follow this pattern:

• τα ελληνικά – Greek
• τα αγγλικά – English
• τα γαλλικά – French

Historically, this is like saying “the Greek things/words”, and it has become the normal way to refer to the language as a whole. So:

• μιλάω ελληνικά = I speak Greek
• στην τάξη μιλάμε μόνο ελληνικά = in class we speak only Greek

In Greek, many activities are expressed with κάνω (“do/make”) + a noun:

• κάνω βιντεοκλήση = make/do a video call
• κάνω τηλεφώνημα = make a phone call
• κάνω διάλειμμα = take a break

So όταν κάνουμε βιντεοκλήση literally = when we make a video call.

You can also use a verb like μιλάω:

• όταν μιλάμε με βίντεο = when we talk on video
  But κάνω βιντεοκλήση is the most natural and direct translation of “do/make a video call”.

In Greek, for repeated, habitual actions in the present or general time, you use όταν + present indicative, not όταν θα…:

• Όταν κάνουμε βιντεοκλήση, μιλάμε ελληνικά.
  = Whenever/when we (normally) make a video call, we speak Greek.

If you said:

• Όταν θα κάνουμε βιντεοκλήση…

it would sound like talking about one specific future event and is usually avoided in standard Greek; you’d say instead:

• Όταν κάνουμε βιντεοκλήση αύριο, θα μιλήσουμε ελληνικά.
  (Present after όταν, future θα μιλήσουμε in the main clause.)

Greek present tense covers both:

• Simple present: I speak / I communicate
• Present continuous: I am speaking / I am communicating

So:

• επικοινωνώ can mean I communicate or I am communicating, depending on context.
• κάνουμε can be we do / we are doing.

English makes a strict distinction between simple and continuous; Greek generally does not in the present tense. Aspect differences appear more clearly in the past / future (e.g. έκανα vs έκανα, θα κάνω vs θα κάνω with different aspects), but in this sentence plain present is enough.

Greek word order is fairly flexible, as long as the relationships between words remain clear. Variants of your sentence include:

• Επικοινωνώ μόνο στα ελληνικά με τη φίλη μου στο σπίτι όταν κάνουμε βιντεοκλήση.
• Στο σπίτι, μόνο στα ελληνικά επικοινωνώ με τη φίλη μου όταν κάνουμε βιντεοκλήση.
• Με τη φίλη μου στο σπίτι επικοινωνώ μόνο στα ελληνικά όταν κάνουμε βιντεοκλήση.

They all keep essentially the same meaning, though shifting pieces slightly changes emphasis:

• Putting μόνο στα ελληνικά earlier emphasizes the language.
• Putting στο σπίτι first emphasizes the location.

The original word order is clear and very natural.

Approximate pronunciation (stress in CAPS):

• επικοινωνώ → e‑pi‑ki‑no‑NO
  /e.pi.ki.noˈno/

• βιντεοκλήση → vi‑de‑o‑KLI‑si
  /vi.ðe.oˈkli.si/

Notes:

• The ν in επικοινωνώ is pronounced; it links -κι-νο-νο smoothly.
• β is pronounced like English v.
• δ (in βιντεοκλήση) is like the th in then, not like English d.