Ancient Greek Accentuation, the article

See Greek Accents for an overview.

The forms which begin with vowel (ὁ, ἡ, οἱ, αἱ) are proclitics.

All other nominative and accusative forms are oxytone.

All genitive and dative forms are perispomenon.

Num	Case	Masc	Fem	Neut
Sg	Nom	ὁ	ἡ	τό
	Acc	τόν	τήν	τό
	Gen	τοῦ	τῆς	τοῦ
	Dat	τῷ	τῇ	τῷ
Pl	Nom	οἱ	αἱ	τά
	Acc	τούς	τάς	τά
	Gen	τῶν	τῶν	τῶν
	Dat	τοῖς	ταῖς	τοῖς

These rules also hold for the dual:

Num	Case	Masc	Fem	Neut
Dl	Nom/Acc	τώ	τώ	τώ
	Gen/Dat	τοῖν	τοῖν	τοῖν