CASE, continued

For reference, here are the declensions of the definite article and three typical nouns, one masculine, one feminine, and one neuter.  Note that the masculine and neuter nouns and definite articles have several similarities.

     singular      plural
nominative ὁ ἄνθρωπος οἱ ἄνθρωποι
genitive τοῦ ἀνθρώπου τῶν ἀνθρώπων
dative τῷ ἀνθρώπῳ τοῖς ἀνθρώποις
accusative τὸν ἄνθρωπον τοῦς ἀνθρώπους
vocative ἄνθρωπε ἄνθρωποι
 
nominative ἡ φωνή αἱ φωναί
genitive τῆς φωνῆς τῶν φωνῶν
dative τῇ φωνῇ ταῖς φωναῖς
accusative τὴν φωνήν τὰς φωνάς
vocative φωνή φωναί
 
nominative τὸ ἆθλον τὰ ἆθλα
genitive τοῦ ἄθλου τῶν ἄθλων
dative τῷ ἄθλῳ τοῖς ἄθλοις
accusative τὸ ἆθλον τὰ ἆθλα
vocative ἆθλον ἆθλα

In very old Greek, such as the Iliad and the Odyssey, another number, the dual, was used to refer to pairs of objects.  It was little used in most classical Greek.

Vocative case was used less and less as time went on.  It and dative have disappeared and are not used in modern Greek.