Nominative

The Ancient Greek nominative, like the Proto-Indo-European nominative, is used for the subject and for things describing the subject (predicate nouns or adjectives):

• Σωκράτης γὰρ σοφὸς ἦν καὶ δίκαιος.^[1]

Sōkrátēs gàr sophòs ên kaì díkaios.

"For Socrates was wise and just."

Vocative

The vocative is used for addressing people or things. It is frequently the same as the nominative in the singular and always the same in the plural.

• ἀληθῆ λέγεις, ὦ Σώκρατες^[2]

alēthê légeis, ô Sṓkrates

"What you say is true, Socrates."

Accusative

The accusative is used for the object of a verb, and also after prepositions. After prepositions it is often used for the destination of motion:

• πέμπουσιν ἐς Κρήτην ἀγγέλους^[3]

pémpousin es Krḗtēn angélous

"They send messengers to Crete."

Genitive

The Ancient Greek genitive can often be translated with the preposition "of" or the English possessive case:

• ἡ τοῦ Καίσαρος γυνή.^[4]

hē toû Kaísaros gunḗ.

"The wife of Caesar."

It is also used after prepositions, especially those which mean "from":

• ἀπῆλθεν ἐκ τῆς ἀγορᾶς.^[5]

apêlthen ek tês agorâs.

"He went away from the market-place."

Dative

The Ancient Greek dative corresponds to the Proto-Indo-European dative, instrumental, or locative. When it corresponds to the dative, it expresses the person or thing that is indirectly affected by an action, and can often be translated with the prepositions "to" or "for":

• λέγει τὴν μαντείαν τῷ Σωκράτει.^[6]

légei tḕn manteían tôi Sōkrátei.

"He tells the oracle to Socrates."

When the dative corresponds to the Proto-Indo-European instrumental, it expresses the thing with which something is done, and can often be translated by the preposition "with":

• ἔβαλλέ με λίθοις^[7]

éballé me líthois

"He was hitting me with stones."

When the dative corresponds to the Proto-Indo-European locative case (this is often the case when it is used with prepositions), it expresses location (sometimes figuratively) or time, and can often be translated by "in", "at", or "on":

• τρίτῳ ἔτει ὡμολόγησαν Ἀθηναίοις.^[8]

trítōi étei hōmológēsan Athēnaíois.

"In the third year they came to an agreement with the Athenians."

The dative is also frequently used after prepositions, such as ἐν (en) "in":

• ἐν τῇ μάχῃ ἀπέθανεν.^[9]

en têi mákhēi apéthanen.

"He died in the battle."

Accent of strong and weak cases

For first- and second-declension nouns accented on the ultima and third-declension nouns with a single-syllable stem, the strong cases (nominative and accusative) have one type of accent, and the weak cases (genitive and dative) have another.

Specifically, the first- and second-declension nouns have acute (´) in the strong cases, but circumflex (ˆ) in the weak cases. Third-declension nouns have the accent on the stem in the strong cases, but the ending in the weak cases.

Both of these patterns can be summarized by a single rule suggested by Paul Kiparsky: pre-ending accent in the strong cases and post-stem accent in the weak cases.^[10]

For first- and second-declension nouns, Kiparsky's rule is more complex. The thematic vowel (ο or ᾱ) counts as neither stem nor ending, but alternates between the two depending on which accent is considered. For post-stem accent, it counts as part of the ending; for pre-ending accent, it counts as part of the stem.

First declension

The first declension or alpha declension is considered thematic, with long alpha (ᾱ) at the end of the stem, though it is derived from original athematic Indo-European forms. In Attic Greek, this changes to η everywhere except after ε, ι or ρ. The first declension includes mostly feminine nouns, but also a few masculine nouns, including agent nouns in -της, patronyms in -ίδης, and demonyms.

The first-declension genitive plural always takes a circumflex on the last syllable. In Homeric Greek the ending was -άων (ᾱ) or -έων (through shortening from *-ηων). -έων was contracted to -ῶν in Attic.^[11]

Second declension

The second or omicron declension is thematic, with an -ο or -ε at the end of the stem. It includes one class of masculine and feminine nouns and one class of neuter nouns.

When a second-declension noun is accented on the ultima, the accent switches between acute for the nominative, accusative, and vocative, and circumflex for the genitive and dative. The only exceptions are Attic-declension and contracted nouns.

Third declension

The third declension group includes masculine, feminine and neuter nouns. It is an athematic declension that lacks the standard thematic vowels of the two thematic declensions above. This results in varied and often complex phonemic interactions between stem and ending, especially so between adjacent consonants, that often make these nouns appear to be highly irregular compared to their straightforward thematic counterparts.

These nouns in the nominative singular end with the vowels α, ι, υ, ω or with the consonants ν, ρ, ς (ξ, ψ). They form the genitive case with -ος, -ως or -ους.

Third-declension nouns have one, two, or three stems, unlike first- and second-declension nouns, which always have only one stem. Each stem is used in different case-and-number forms. In nouns with two stems, the stem with the long vowel is called the strong stem, while the stem with the short vowel is called the weak stem. The strong stem is found at the nominative singular, and the weak stem in the genitive singular.

• ἡγεμών (long vowel, strong stem: nominative singular)

  ἡγεμόνος (short vowel, weak stem: genitive singular)

Diminutive suffixes

New nouns may be formed by suffix addition. Sometimes suffixes are added on top of each other:

• βῐ́βλος bíblos "papyrus"
  • βιβλίον biblíon "book"
  • βιβλάριον, βιβλιάριον, βιβλαρίδιον, βιβλιδάριον "small scroll"^[18]

    biblárion, bibliárion, biblarídion, biblidárion

  • βιβλίδιον biblídion "petition"