In short

Greek nouns change their form according to their job in the sentence. Modern Greek has four cases - ονομαστική (nominative), γενική (genitive), αιτιατική (accusative), κλητική (vocative) - and there is no dative. This lesson takes the two you need first: the nominative marks the subject, the accusative marks the direct object. Because the ending and the article carry that information, word order is free: both Ο Νίκος βλέπει τον Γιώργο and Τον Γιώργο βλέπει ο Νίκος mean that Nikos is doing the seeing.

The second half is a spelling habit that goes with the accusative: the little words τη(ν), μια(ν), δε(ν), μη(ν) keep their final -ν before a vowel and before κ, π, τ, ξ, ψ, μπ, ντ, γκ, τσ, τζ, and drop it elsewhere - τη Δευτέρα but την Τρίτη.

The rule

Four cases, no dative. Every noun, article, adjective and pronoun has four forms per number. The nominative names the subject, the genitive shows possession (lesson 31), the accusative marks the direct object and follows almost every preposition (lesson 15), and the vocative is for calling someone (lesson 21). The ancient dative is gone; it survives only in frozen expressions such as εν τω μεταξύ (“in the meantime”), εντάξει (“all right”) and δόξα τω Θεώ (“thank God”), which are fossils, not a living case - learn them as single words.

The nominative is the subject. Ο σκύλος τρώει means “the dog is eating”. The article ο and the ending -ος together say “this is the one doing it”.

The accusative is the direct object. Βλέπω τον σκύλο - “I see the dog”. The masculine article changes ο -> τον and the noun loses its final -ς: ο σκύλος -> τον σκύλο. The feminine article changes η -> τη(ν) but the noun itself does not change in the singular: η Μαρία -> τη Μαρία. Neuter nouns look identical in both cases: το παιδί is subject and object alike, so the verb and the context tell you which.

Case beats word order. English relies on position (“the dog bites the man” is not “the man bites the dog”). Greek relies on the form, so the object may be moved to the front for emphasis without any change of meaning:

• Ο Νίκος βλέπει τον Γιώργο. - Nikos sees Giorgos. (neutral)
• Τον Γιώργο βλέπει ο Νίκος. - It is Giorgos that Nikos sees. (Giorgos in focus)

In both, τον Γιώργο is accusative and ο Νίκος is nominative, so the roles never move. Read the article first, not the position.

After είμαι, the complement stays nominative. είμαι, γίνομαι and similar verbs do not take an object; they link two nominatives. Η Μαρία είναι δασκάλα, Ο Κώστας είναι καλός μαθητής. Professions and nationalities usually come with no article at all after είμαι (lesson 3).

Time phrases with no preposition are accusative. Where English says “on Monday” or “in the morning”, Greek uses a bare accusative: τη Δευτέρα, την Τρίτη, το πρωί, το βράδυ, τις Κυριακές, αυτή την εβδομάδα.

The final -ν rule (ο κανόνας του τελικού ν). Four small words end in -ν only when the next word begins with a sound that “welcomes” it:

• the feminine accusative article τη(ν) and the weak pronoun τη(ν) (“her, it”)
• the feminine indefinite μια(ν) (the -ν here is optional in practice)
• the negatives δε(ν) and μη(ν)

They keep -ν before a vowel and before κ, π, τ, ξ, ψ, μπ, ντ, γκ, τσ, τζ. They drop it before every other consonant: β, γ, δ, ζ, θ, λ, μ, ν, ρ, σ, φ, χ. The reason is pronunciation - that -ν voices the stop that follows it, so την Τρίτη is heard as if the second word began with ντ, and δεν πάω as if it began with μπ.

The masculine words are an exception by convention. Modern school grammar writes the masculine accusative τον, έναν and αυτόν always with -ν, whatever follows, so that they are never confused with the neuter το or the feminine τη: τον φίλο, τον δρόμο, έναν καφέ, έναν χάρτη. So the rule you actually have to think about is the feminine one.

Forms & patterns

The definite article - all four cases

The vocative takes no article at all in Modern Greek: Μαρία!, Γιώργο!, παιδιά!

The indefinite article (singular only - there is no plural form)

Article plus noun, the two cases side by side

τη φίλη drops the -ν because φ is not in the keep-list; την Πέμπτη keeps it because π is.

Full paradigm, masculine: ο άνθρωπος (watch the accent move to the second syllable in both genitives and in the accusative plural)

Full paradigm, feminine: η θάλασσα (the accent moves to the ending in the genitive plural)

Full paradigm, neuter: το παιδί (nominative and accusative are identical)

The final -ν in practice

Examples

Common mistakes

• Βλέπω ο Γιώργος. -> Βλέπω τον Γιώργο. - the direct object is accusative; ο is only ever a subject.
• Η Μαρία ρωτάει η Άννα. -> Η Μαρία ρωτάει την Άννα. - two nominatives leave the sentence with no object at all.
• Τον Γιώργο βλέπει τον Νίκο. -> Τον Γιώργο βλέπει ο Νίκος. - fronting the object does not turn the subject into an accusative.
• Είμαι τον δάσκαλο. -> Είμαι δάσκαλος. - είμαι links two nominatives and takes no object.
• την Δευτέρα -> τη Δευτέρα - δ is not in the keep-list, so the -ν goes.
• τη Τρίτη -> την Τρίτη - τ is in the keep-list, so the -ν stays.
• τη ώρα -> την ώρα - before any vowel the -ν always stays.
• Αγοράζω ένα καφέ. -> Αγοράζω έναν καφέ. - masculine accusative is έναν; ένα here would make it neuter.
• Δε μπορώ σήμερα. -> Δεν μπορώ σήμερα. - μπ keeps the -ν.
• Μη ανησυχείς! -> Μην ανησυχείς! - a following vowel keeps the -ν.
• Στη Ελλάδα. -> Στην Ελλάδα. - στη(ν) is σε + τη(ν) and follows the same rule.

Tips

• Read the article, not the position. ο/η/οι/τα in the nominative slots, τον/τη/τους/τις in the accusative - once you see τον, you know that word is not the subject, wherever it sits.
• Learn every new noun with its article (ο δρόμος, η πόρτα, το τραπέζι). The article is what you will actually have to change, and it is where the -ν rule lives.
• A memory hook for the keep-list: they are the stops and the affricates - κ, π, τ, their compounds ξ (= κ+σ) and ψ (= π+σ), and the digraphs μπ, ντ, γκ, τσ, τζ. Everything you can hum or hiss (β, γ, δ, ζ, θ, λ, μ, ν, ρ, σ, φ, χ) takes no -ν.
• The days of the week are a free daily drill: τη Δευτέρα, την Τρίτη, την Τετάρτη, την Πέμπτη, την Παρασκευή, το Σάββατο, την Κυριακή.
• Do not hunt for a preposition in time phrases - “on Monday” is just τη Δευτέρα, bare accusative.
• Say it out loud before you write it. If the -ν turns the following κ, π, τ into a γκ, μπ, ντ sound (την Τρίτη, δεν πάω), it belongs there; if the words run on smoothly (τη θάλασσα, δε φεύγω), it does not.
• Do not worry about masculine τον and έναν: write them with -ν every single time. You will also see δεν and την written with -ν everywhere in informal texts and online - that is common practice, but the rule above is what is expected in careful writing.