Learn Hardcore Greek: Έχεις τηλέφωνο;

No. Greek usually drops subject pronouns because the verb ending shows the person. Έχεις τηλέφωνο; already means “Do you have a phone?” You’d add Εσύ only for emphasis: Εσύ έχεις τηλέφωνο; (Do you have a phone, as opposed to someone else?).

Why is there no article before τηλέφωνο?

Greek often omits the indefinite article with έχω when speaking generally about having something. Έχω/Έχεις τηλέφωνο; naturally means “I/you have a phone?” in the general, indefinite sense. With the definite article (το), Έχεις το τηλέφωνο; means “Do you have the phone (we’re referring to)?”

Can I say Έχεις ένα τηλέφωνο;? What’s the nuance?

Yes. Έχεις ένα τηλέφωνο; is fine and can feel a bit more specific or practical (as in “Do you have a phone I could use/borrow?”). The version without ένα is the most neutral, general way to ask if someone has a phone at all.

How do I ask formally or more politely?

Use the plural/formal: Έχετε τηλέφωνο; To soften it further, add μήπως (“by any chance”): Μήπως έχετε τηλέφωνο; (very polite). Informal polite: Μήπως έχεις τηλέφωνο;

Does τηλέφωνο mean mobile or landline? How do I ask specifically?

τηλέφωνο is generic. To be specific:

Έχεις κινητό; — Do you have a mobile (cell phone)?
Έχεις σταθερό; — Do you have a landline? You can also say κινητό τηλέφωνο or σταθερό τηλέφωνο, but in everyday speech people usually shorten them to κινητό / σταθερό.

How do I pronounce Έχεις τηλέφωνο;?

Roughly: eh-HEES tee-LE-fo-no.

χ is a voiceless “h-like” sound (like German “ich”), not an English “k” or “h”.
η/ει sound like “ee.”
Stress is on Έ- in Έχεις and on -λέ- in τηλέφωνο.

Why is there a semicolon at the end?

In Greek, the semicolon (;) is the question mark. So Έχεις τηλέφωνο; uses Greek punctuation and is just a normal yes/no question.

What case is τηλέφωνο here? What are its core forms?

It’s the direct object, so accusative singular. For neuter nouns like τηλέφωνο, nominative and accusative singular look the same:

Nominative/Accusative: το τηλέφωνο
Genitive: του τηλεφώνου Plural:
Nominative/Accusative: τα τηλέφωνα
Genitive: των τηλεφώνων

How do I negate it?

Statement: Δεν έχω τηλέφωνο. — I don’t have a phone.
Question: Δεν έχεις τηλέφωνο; — Don’t you have a phone? (often expressing surprise)

How do I answer yes or no naturally?

Yes: Ναι, έχω. (or Ναι, έχω τηλέφωνο.)
No: Όχι, δεν έχω. You can add detail: Ναι, έχω κινητό, όχι σταθερό.

Could this also mean “Do you have a phone number?” How do I ask for someone’s number?

In some contexts, Έχεις τηλέφωνο; can be understood as “Do you have a (phone) number?” but to ask clearly for someone’s number say:

Ποιο είναι το τηλέφωνό σου; — What’s your phone number?
Polite/formal: Μπορώ να έχω το τηλέφωνό σας; Note the accent shift with the clitic: το τηλέφωνό σου/σας (accent on -νό).

Can I switch the word order, e.g., Τηλέφωνο έχεις;?

Yes. Τηλέφωνο έχεις; is possible and puts focus on τηλέφωνο, often used for emphasis or mild surprise. The neutral order is Έχεις τηλέφωνο;

How would I say this in the past or the future?

Past: Είχες τηλέφωνο; — Did you have a phone?
Future: Θα έχεις τηλέφωνο; — Will you have a phone?
I forms: Είχα τηλέφωνο. / Θα έχω τηλέφωνο.

How do I say “to call (someone)” and how does it relate to τηλέφωνο?

The verb is τηλεφωνώ (σε κάποιον): Θα σου τηλεφωνήσω. — I’ll call you. A very common colloquial phrase is παίρνω τηλέφωνο: Σε πήρα τηλέφωνο χθες. — I called you yesterday.