In short

Asking a yes/no question in Greek costs you nothing at all: you say the statement, you let your voice rise at the end, and you write the Greek question mark «;». Nothing moves, and nothing is added - there is no inversion and no equivalent of English “do”. Μιλάς ελληνικά. is “You speak Greek.” and Μιλάς ελληνικά; is “Do you speak Greek?”

For open questions Greek has a small closed set of question words. Four are invariable adverbs - πού, πότε, πώς, γιατί - and τι is an invariable pronoun. Two more are pronouns that behave like adjectives and agree with what they ask about: ποιος, ποια, ποιο (“which, who”) and πόσος, πόση, πόσο (“how much, how many”). Whichever you use, it stands first in the clause, the verb normally comes straight after it, and the subject, if you name one, comes last: Τι κάνει ο Γιάννης;

The rule

1. Yes/no questions. Keep the word order of the statement and change only two things: the intonation (a rise on the last stressed syllable) and the final punctuation mark.

• Ο καφές είναι ζεστός. -> Ο καφές είναι ζεστός;
• Μένετε στην Αθήνα. -> Μένετε στην Αθήνα;

Do not look for an auxiliary to move to the front. English builds do you speak, are you speaking, have you spoken; Greek builds nothing. The one-word answers are ναι and όχι, and a natural fuller answer repeats the verb rather than the auxiliary: Μιλάς ελληνικά; - Ναι, μιλάω λίγο.

2. The question mark is «;». It looks like an English semicolon and sits on the same key. Every Greek question ends with it, direct and short alike: Τι ώρα είναι; Πόσο κάνει; An English «?» at the end of a Greek sentence is a spelling error.

3. Open questions: the question word goes first. The order is

question word - verb - (subject) - (rest)

• Πού μένει η Μαρία;
• Πότε φεύγει το τρένο;
• Τι θέλουν τα παιδιά;

Note the subject after the verb. English says “Where does Maria live?”; Greek simply lets the subject follow, because the question word has taken the front position. And since Greek drops pronoun subjects (lesson 5), most questions have no subject at all: Πού μένεις; The one question word that also tolerates a subject in front of the verb is γιατί: Γιατί ο Γιάννης δεν ήρθε; is as good as Γιατί δεν ήρθε ο Γιάννης;

4. Invariable versus declined. τι, πού, πότε, πώς and γιατί never change their form. ποιος and πόσος are pronouns with endings and must agree in gender, number and case with the noun they stand for or accompany:

• Ποιος μιλάει; (a man, subject -> masculine nominative)
• Ποιον ρωτάς; (a man, object -> masculine accusative)
• Ποια βιβλία διαβάζεις; (neuter plural)
• Πόσα αδέλφια έχεις; (neuter plural)

The genitive forms of these pronouns (ποιου and ποιανού, πόσου - plus the formal τίνος, which belongs to the learned τις) come with the genitive case in lesson 31; here you need the nominative for subjects and the accusative for objects and for the noun after a preposition.

5. τι against ποιο. τι asks an open question - the field of possible answers is unlimited. ποιος/ποια/ποιο asks you to pick out of a set that both speakers already have in mind.

• Τι θέλεις; = What do you want? (anything at all)
• Ποιο θέλεις; = Which one do you want? (of these, on the table, in the photo)

6. πόσος and the adverb πόσο. As a pronoun πόσος agrees: Πόσες μέρες; Πόσοι φοιτητές; The neuter πόσο also works as a plain adverb of degree, and that is the form frozen into the shopping question Πόσο κάνει; (“How much is it?”), plural Πόσο κάνουν;

7. The tag έτσι δεν είναι; English tags copy the verb (“you’re Greek, aren’t you?”; “she came, didn’t she?”). Greek has one fixed tag for all of them: έτσι δεν είναι; Colloquially a bare ε; does the same job.

Forms & patterns

The invariable question words

τι is used for both subject and object without changing: Τι έγινε; (subject) - Τι είδες; (object).

ποιος, ποια, ποιο - “who / which”

Ενικός (singular):

Πληθυντικός (plural):

Every cell here is a single syllable - ποι- is pronounced as one sound - so none of them takes an accent. The masculine accusative singular keeps a final -ν (ποιον) exactly as the article τον does, by the rule you met in lesson 8; the plural ποιους has no -ν to keep.

πόσος, πόση, πόσο - “how much, how many”

Ενικός (singular):

Πληθυντικός (plural):

The singular asks about quantity of an uncountable thing (Πόση ζάχαρη;), the plural about a number of countable things (Πόσα ευρώ;).

Statement, yes/no question, open question

Examples

Common mistakes

• Κάνεις τι; -> Τι κάνεις; - the question word opens the clause; leaving it at the end sounds like a startled echo, not a normal question.
• Κάνεις μιλάς ελληνικά; -> Μιλάς ελληνικά; - there is no “do” auxiliary to borrow. The verb κάνω means “do/make” as a real action, never as a question helper.
• Μιλάς ελληνικά? -> Μιλάς ελληνικά; - the Greek question mark is «;», not «?».
• Που μένεις; -> Πού μένεις; - the interrogative πού carries an accent; the unaccented που is the relative “who/which/that” (the pronunciation guide’s lesson on punctuation and the disambiguating accent sets out the whole pair).
• Πως σε λένε; -> Πώς σε λένε; - same pair: πώς asks “how?”, πως introduces “that”.
• Ποιος θέλεις; -> Ποιον θέλεις; - the person asked about is the object of θέλω, so the pronoun goes into the accusative.
• Ποια είναι το πρόβλημα; -> Ποιο είναι το πρόβλημα; - ποιος agrees with the noun it refers to, and πρόβλημα is neuter.
• Πόσο αδέλφια έχεις; -> Πόσα αδέλφια έχεις; - πόσος is a full adjective-like pronoun; with a countable neuter plural it is πόσα.
• Ποιο θέλεις; with nothing in view -> Τι θέλεις; - ποιο presupposes a set both speakers already have in mind; with the field wide open the question word is τι. Once the options are actually named, either one is normal Greek: Τι θέλεις, τσάι ή καφέ;
• Πού είναι ο Γιάννης πηγαίνει; -> Πού πηγαίνει ο Γιάννης; - one verb, straight after the question word, with the subject behind it.

Tips

• Practise the melody, not just the words. In a yes/no question the pitch climbs on the last stressed syllable and stays up; in the matching statement it falls. With no inversion and no auxiliary, intonation is the only thing your listener has to go on.
• On a keyboard, the Greek question mark is simply the semicolon key while you are in the Greek layout. If your text shows «?» at the end of Greek sentences, your layout slipped.
• Answer with the verb, not with an auxiliary: Ήρθες; - Ναι, ήρθα. A bare ναι is fine too, but “Yes, I did” has no Greek translation of that shape.
• A quick test for τι against ποιο: if you could point at the choices, use ποιο (and make it agree). If the answer could be anything in the world, use τι.
• Learn Πώς σε λένε; and Πόσο κάνει; as whole units. Greek uses “how” where English uses “what” for names, and the frozen neuter πόσο for prices.
• γιατί does double duty: it asks “why?” and it answers “because”. Γιατί άργησες; - Γιατί έχασα το λεωφορείο.
• έτσι δεν είναι; never changes, whatever the verb of the main clause was. That makes it easier than the English tag system, so use it freely.