Interrogative Determiners: ποιος, πόσος, τι | Greek Grammar

Some question words stand alone — who?, when?, why?. Others lean on a noun: which *train?, how many **days?, what **colour? Greek has three of the second kind, and they behave in a way English gives you no preparation for. *ποιος and πόσος are inflected adjectives, so you cannot ask the question until you have decided the noun's gender, number and case. τι is frozen. And all three — unlike the demonstratives they otherwise resemble — take a bare noun with no article.

ποιος: which one, out of a set

ποιος / ποια / ποιο asks the hearer to pick a member out of a set that both of you can already see or have already talked about. It declines exactly like a -ος / -η / -ο adjective, except that the whole stem is pronounced as one syllable, which is why none of these forms is written with an accent.

	Masculine	Feminine	Neuter
Nom. sg.	ποιος	ποια	ποιο
Gen. sg.	ποιου	ποιας	ποιου
Acc. sg.	ποιον	ποια	ποιο
Nom. pl.	ποιοι	ποιες	ποια
Gen. pl.	ποιων (one form for all three genders)
Acc. pl.	ποιους	ποιες	ποια

Ποιο λεωφορείο πάει στην Ακρόπολη;

pio leoforío pái stin Akrópoli;

Which bus goes to the Acropolis?

Ποιον γιατρό μου συνιστάς;

pion yatró mu sinistás;

Which doctor would you recommend?

Ποιου παιδιού είναι αυτή η ζακέτα;

piu pedhiú íne aftí i zakéta;

Which child does this cardigan belong to?

Με ποιο τρένο θα έρθεις;

me pio tréno tha érthis;

Which train are you coming on?

That last one shows the ordinary case behaviour: after a preposition the whole phrase goes accusative, so it is με ποιον φίλο, σε ποια πόλη, από ποιο μαγαζί. The details of interrogatives after prepositions are on interrogatives with prepositions.

The three genitives

The genitive of ποιος has three live forms, and they are not interchangeable in register:

ποιου / ποιας / ποιων — the neutral standard, at home in speech and writing alike.
ποιανού / ποιανής / ποιανών — (informal), very frequent in everyday speech, especially about ownership.
τίνος / τίνων — (formal), a survival from the older learned language; today it is found mostly standing alone in careful writing and journalism, rarely in front of a noun.

Ποιανού αμαξιού είναι αυτός ο συναγερμός;

pianú amaksiú íne aftós o sinayermós;

Whose car is that alarm coming from? (everyday speech)

Τίνος είναι η ευθύνη για το ατύχημα;

tínos íne i efthíni ya to atíchima;

Whose responsibility is the accident? (formal / written)

πόσος: how much, how many

πόσος / πόση / πόσο is a perfectly regular -ος / -η / -ο adjective with the accent fixed on the first syllable. English how much and how many are two expressions precisely because English marks countability on the quantifier; Greek marks it on the noun, so one word covers both and the noun's number does the work.

	Masculine	Feminine	Neuter
Nom. sg.	πόσος	πόση	πόσο
Gen. sg.	πόσου	πόσης	πόσου
Acc. sg.	πόσο(ν)	πόση	πόσο
Nom. pl.	πόσοι	πόσες	πόσα
Gen. pl.	πόσων
Acc. pl.	πόσους	πόσες	πόσα

Πόσες μέρες θα μείνεις στη Ρόδο;

póses méres tha mínis sti Ródho;

How many days are you staying on Rhodes?

Πόσο κόσμο περιμένεις απόψε;

póso kózmo periménis apópse;

How many people are you expecting tonight?

Πόσα δωμάτια έχει το σπίτι;

pósa dhomátia échi to spíti;

How many bedrooms does the house have?

Two things worth pinning down. κόσμος ("people") is grammatically a masculine singular collective, so how many people comes out as the singular πόσο κόσμο — the Greek asks how much crowd. And πόσων turns up in the standard way of asking someone's age, a genitive-of-measure phrase:

Πόσων χρονών είναι το μωρό;

póson chronón íne to moró;

How old is the baby?

In casual speech you will also hear πόσο χρονών; both circulate, and the genitive πόσων is what careful writing uses.

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Two Greek question words make you commit to a gender before you can ask anything at all: ποιος and πόσος. You cannot ask "which one?" about a bag without knowing that τσάντα is feminine. That is a strong practical argument for learning every noun together with its article from the very first day.

Alongside the determiner there is an invariable adverb **πόσο** ("how much", modifying a verb or adjective) — the one in *Πόσο κάνει;* — which never agrees with anything. That split runs through the whole quantifier series and is treated on [πολύς, λίγος, αρκετός](/grammar/greek/determiners/quantifier-polys).

τι: frozen, and open-ended

τι never changes, in any gender, number or case: τι ώρα, τι χρώμα, τι δουλειά, τι προβλήματα, με τι λεφτά. Where ποιος asks you to choose from a set, τι asks with the field wide open — it wants a kind, not a member.

Τι ώρα κλείνει το φαρμακείο;

ti óra klíni to farmakío;

What time does the chemist's close?

Τι δουλειά κάνει ο πατέρας σου;

ti dhuliá káni o patéras su;

What does your father do for a living?

Τι είδους μουσική ακούς;

ti ídhus musikí akús;

What sort of music do you listen to?

τι είδους ("what kind of") is worth learning as a chunk — it is invariable and slots in front of any noun. Note also that τι is the word Greek uses in front of category nouns: ώρα, μέρα, χρώμα, νούμερο, όνομα, δουλειά. Τι μέρα είναι σήμερα; asks which day of the week it is; Ποια μέρα σε βολεύει; asks you to choose one out of several.

ποιος or τι?

The line is closed set versus open field, and it is the one distinction English refuses to make consistently — English what covers both.

Τι κρασί προτιμάς, λευκό ή κόκκινο;

ti krasí protimás, lefkó i kókino;

What wine do you prefer, white or red?

Ποιο κρασί να ανοίξω, το λευκό ή το ροζέ;

pio krasí na aníkso, to lefkó i to rozé;

Which wine shall I open, the white or the rosé?

The first asks about a type in the abstract — no particular bottles involved. The second is asked with two specific bottles on the counter, and that is exactly when Greek switches to ποιο. The same contrast is what makes Ποιο είναι το όνομά σου; the natural way to ask someone's name: a name is one item picked from the set of names, not a category. The fuller treatment of the pair, including their standalone pronoun uses, is on τι or ποιος and interrogative pronouns.

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Ask yourself whether the answer is one of these or what sort. One of these — the bottles on the counter, the days in the diary, the children in the room — takes ποιος. What sort, no set in view, takes τι. When both are possible, the choice is real: it tells your listener whether you have a specific set in mind.

No article — and this is where the demonstratives mislead you

Greek demonstratives keep the definite article: αυτό *το βιβλίο*. Interrogative determiners do the opposite — they occupy the determiner slot themselves and take a bare noun: ποιο βιβλίο, πόσα βιβλία, τι βιβλίο. Having just learned the αυτό-το pattern from demonstratives, learners regularly carry it across, and it is the single most common structural error on this page.

There is one construction that looks like a counter-example and is not. Ποιο είναι το πρόβλημα; has the article because το πρόβλημα is the subject of the copula and ποιο is the predicate, standing alone as a pronoun — it is not determining το πρόβλημα at all. Elevated and headline Greek then drops the copula altogether, leaving Ποιο το νόημα; ("What's the point?"), Ποιος ο λόγος;, Ποια η διαφορά; — verbless sentences of a register you meet in print and in rhetorical questions. Neither is the determiner pattern.

One more thing: the question mark and the accent

Greek writes its question mark as a semicolon: Ποιο βιβλίο; not ×Ποιο βιβλίο? This trips up almost everybody at first and is worth deliberate practice — see the Latin question mark. Note also that ποιος, πόσος and τι need no disambiguating accent: unlike πού and πώς, which are spelled with a tonos to keep them apart from the relative που and the conjunction πως, these three have no homograph to be confused with. The accent rules for question words are on question-word accents, and the shape of the questions themselves on wh-questions.

Finally, τι and πόσος do double duty in exclamations — Τι ωραία θέα!, Πόσα λεφτά! — with the same forms and no question mark; that use is on exclamatory τι and πόσο, and their declarative answers, τέτοιος and τόσος, on τέτοιος and τόσος.

Common Mistakes

1. Using τι where the answer must come out of a set. English what hides the distinction, so learners default to τι.

❌ Τι από τα δύο φορέματα σου αρέσει;

Incorrect — choosing from a stated set requires ποιος: Ποιο από τα δύο φορέματα;

✅ Ποιο από τα δύο φορέματα σου αρέσει περισσότερο;

pio apó ta dhío forémata su arési perisótero;

Which of the two dresses do you like better?

2. Adding the article, on the model of αυτό το βιβλίο.

❌ Ποιο το βιβλίο διαβάζεις;

Incorrect — an interrogative determiner takes a bare noun: Ποιο βιβλίο διαβάζεις;

✅ Ποιο βιβλίο διαβάζεις τώρα; Θέλω κι εγώ κάτι καλό.

pio vivlío dhiavázis tóra; thélo ki eghó káti kaló

Which book are you reading at the moment? I want something good too.

3. Leaving ποιος in the nominative after a preposition.

❌ Με ποιος πήγες στον γάμο;

Incorrect — after a preposition the form is accusative: Με ποιον πήγες;

✅ Με ποιον πήγες τελικά στον γάμο της Ελένης;

me pion píyes teliká ston ghámo tis Elénis;

Who did you end up going to Eleni's wedding with?

4. Using ποιος as a relative pronoun. English who is both a question word and a relative; Greek's relative is που.

❌ Ο άντρας ποιος μένει από πάνω παίζει πιάνο στις δύο τη νύχτα.

Incorrect — the relative pronoun is που: Ο άντρας που μένει από πάνω.

✅ Ο άντρας που μένει από πάνω παίζει πιάνο στις δύο τη νύχτα.

o ándras pu méni apó páno pézi piáno stis dhío ti níchta

The man who lives upstairs plays the piano at two in the morning.

5. Asking a name with τι. Τι είναι το όνομά σου; is not ungrammatical — it is a different question. τι asks what kind of thing something is (Τι είναι ο πατέρας σου; = what does he do for a living), so it is heard as asking what sort of thing your name is, not what you are called.

✅ Τι είναι αυτό, όνομα ή επώνυμο;

ti íne aftó, ónoma i epónimo;

What is that — a first name or a surname? (τι asks what category it falls into)

✅ Ποιο είναι το όνομά σου; Θέλω να το γράψω σωστά.

pio íne to ónomá su; thélo na to ghrápso sostá

What's your name? I want to spell it correctly. (and in ordinary speech, simply Πώς σε λένε;)

Key Takeaways

ποιος and πόσος decline like ordinary -ος / -η / -ο adjectives; τι is frozen. So the noun's gender, number and case have to be settled before the question can be built.
ποιος picks a member out of a set in view; τι asks for a kind, with no set implied. English what covers both, which is why the choice has to be made deliberately.
The forms of ποιος carry no accent — the whole stem is one syllable — while πόσος keeps its accent on the first syllable throughout.
The genitive has three registers: ποιου (neutral), ποιανού (informal), τίνος (formal).
Interrogative determiners take a bare noun: ποιο βιβλίο, never ×ποιο το βιβλίο. This is the opposite of the demonstratives, which keep the article.
Greek's question mark is the semicolon (;), and none of these three words needs a disambiguating accent the way πού and πώς do.

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