In short

When you call someone by name in Greek, the name changes shape. You talk about Γιώργος, but you talk to Γιώργο. That fourth case is the κλητική (vocative), and it is the only case that is never introduced by an article: never ο Γιάννη, just Γιάννη.

The work is small and almost entirely masculine. Feminine and neuter nouns look exactly the same when you address them (Μαρία, κυρία, παιδί). Masculine nouns in -ος take -ε (φίλε, κύριε, γιατρέ), except short first names, which take -ο (Γιώργο, Νίκο, Πέτρο). Masculine nouns in -ας and -ης simply drop the final -ς (Κώστα, Γιάννη, Μανώλη).

The second half of politeness is the pronoun. Greek has an ordinary T/V distinction: εσύ with second-person-singular verbs for people you are close to, and εσείς with second-person-plural verbs for strangers, officials and older people. Note one detail English speakers regularly miss: with polite εσείς the verb is plural but a predicate adjective describing one person stays singular — Είστε κουρασμένος;

The rule

1. The vocative is a case, and it has no article. Greek nominals have four cases: ονομαστική, γενική, αιτιατική, κλητική. The first three appear with the article (ο φίλος, του φίλου, τον φίλο); the vocative appears bare, usually set off by a comma or an exclamation mark: Φίλε, τι κάνεις; A word like ο Γιάννη is simply not Greek — the article and the vocative cannot coexist.

2. Masculine -ος → -ε. Common nouns, professions and titles in -ος form the vocative in -ε: ο φίλος → φίλε, ο κύριος → κύριε, ο δάσκαλος → δάσκαλε, ο άνθρωπος → άνθρωπε. Oxytone nouns behave the same: ο γιατρός → γιατρέ, ο αδερφός → αδερφέ.

3. But short first names in -ος → -ο. Everyday personal names drop the -ς and end in -ο, which makes the vocative look identical to the accusative: Γιώργος → Γιώργο, Νίκος → Νίκο, Πέτρος → Πέτρο, Χρήστος → Χρήστο, Θάνος → Θάνο. Long or learned names keep the regular -ε (Αλέξανδρος → Αλέξανδρε), and so do surnames in -ος: κύριε Παπαδόπουλε, κύριε Νικολόπουλε.

4. Masculine -ας and -ης just lose the -ς. ο Κώστας → Κώστα, ο άντρας → άντρα, ο Γιάννης → Γιάννη, ο Μανώλης → Μανώλη, ο μαθητής → μαθητή. Nothing else moves: the accent stays where the nominative had it.

5. Feminine and neuter: no change at all. η Μαρία → Μαρία, η κυρία → κυρία, η Ελένη → Ελένη, το παιδί → παιδί, το αγόρι → αγόρι. Only the missing article tells you it is a vocative. In the plural too, the vocative is identical to the nominative for every gender: φίλοι, κυρίες, παιδιά.

6. Titles agree with the name. Both the title and the surname go into the vocative when both are masculine: κύριε Παπαδόπουλε. Feminine surnames in Greek are genitive in form and do not change at all, so the title alone carries the address: κυρία Παπαδοπούλου. Masculine surnames that are themselves genitive-shaped are likewise unchanged: κύριε Δημητρίου, κύριε Αντωνίου.

7. εσύ or εσείς. Use εσύ (verb in the 2nd singular, σου) with family, friends, children, classmates and anyone who has offered it. Use εσείς (verb in the 2nd plural, σας) with strangers on the street, shop and office staff, doctors, teachers, officials, and people noticeably older than you. εσείς is also the plain plural, so the same form covers two situations; the context makes it clear.

8. Plural verb, singular adjective. When εσείς is polite but the person is one, the verb is plural and everything describing that one person is singular and agrees in gender: Είστε κουρασμένος; (to a man) · Είστε κουρασμένη; (to a woman) · Είστε κουρασμένοι; (to several people). The same holds for nouns: Είστε ο κύριος Αντωνίου;

9. Greetings split the same way. Γεια σου / Γεια σας, Τι κάνεις; / Τι κάνετε;, Πώς είσαι; / Πώς είστε; Καλημέρα is the exception: it usually stands on its own, and when it does take a pronoun that pronoun is normally the plural — Καλημέρα σας! The greeting Χαίρετε is polite by itself and is a safe opening with someone you do not know. Do not mix registers inside one sentence: Γεια σας, κύριε Παπαδόπουλε, not Γεια σου, κύριε Παπαδόπουλε.

Forms & patterns

Masculine in -ος: common noun — ο φίλος

Masculine in -ος with a moving accent — ο άνθρωπος

Masculine in -ός: a profession you will call out — ο γιατρός

Masculine in -ας — ο άντρας

Masculine in -ης — ο μαθητής

Feminine: nothing changes — η κυρία

Neuter: nothing changes — το παιδί

First names and surnames (names have no everyday plural, so only the singular is given)

εσύ against εσείς — the verb είμαι and a predicate adjective

Examples

Common mistakes

• Γιώργος, πού είσαι; -> Γιώργο, πού είσαι; — a short first name in -ος has the vocative in -ο; the nominative is only for talking about him.
• Κύριος Παπαδόπουλος, καλημέρα! -> Κύριε Παπαδόπουλε, καλημέρα! — both the title and a surname in -ος take the vocative -ε.
• Ο Γιάννη, τι κάνεις; -> Γιάννη, τι κάνεις; — the vocative never takes an article.
• Φίλο μου, δεν έχεις δίκιο. -> Φίλε μου, δεν έχεις δίκιο. — the -ο vocative belongs to short names only; ordinary nouns in -ος end in -ε.
• Κυρία Παπαδοπούλε! -> Κυρία Παπαδοπούλου! — feminine surnames are genitive in form and never change.
• Μαρίε! / Μαρίο! -> Μαρία! — feminine and neuter nouns have no separate vocative.
• Κύριε, πού μένεις; -> Κύριε, πού μένετε; — a stranger you address as κύριε gets εσείς, not εσύ.
• Είστε κουρασμένοι; (to one person) -> Είστε κουρασμένος; — polite εσείς takes a plural verb but a singular adjective agreeing with that one person.
• Είστε κουρασμένος; (to two friends) -> Είστε κουρασμένοι; — with a real plural the adjective is plural too.
• Γεια σου, κύριε Παπαδόπουλε. -> Γεια σας, κύριε Παπαδόπουλε. — do not mix a polite title with an informal greeting.

Tips

• Learn the vocative as one small habit, not a paradigm: masculine nouns in -ος end in -ε, short masculine names end in -ο, everything else in -ας/-ης loses its -ς, and feminines and neuters stay put.
• If a form makes you hesitate, remember that the vocative of a short name is identical to the accusative: you already know τον Γιώργο, so you already know Γιώργο!
• Watch for the missing article. Hearing a bare noun at the start or end of a sentence is the clearest signal that someone is being addressed.
• When in doubt about the pronoun, start with εσείς. Being slightly too formal is invisible; being too familiar with a stranger is not.
• κύριε and κυρία are far more current in Greek than “sir” and “madam” are in English — they are the normal way to open a question to a stranger, a waiter or a clerk.
• Keep the second accent when a weak pronoun follows a word stressed on its third-from-last syllable: το όνομά σας, το τηλέφωνό σου, ο δάσκαλός μας.
• Greek questions end in the ερωτηματικό «;» — Πώς είστε; Τι κάνετε; — even though it looks like a semicolon.