αυτος

αυτος is usually the third person, personal pronoun.

Singular

Masculine

Feminine

Neuter

Nominative

αυτος

αυτη

αυτο

Genitive

αυτου

αυτης

αυτου

Dative

αυτω

αυτη

αυτω

Accusative

αυτον

αυτην

αυτο

Plural

Masculine

Feminine

Neuter

Nominative

αυτοι

αυται

αυτα

Genitive

αυτων

αυτων

αυτων

Dative

αυτοις

αυταις

αυτοις

Accusative

αυτους

αυτας

αυτα

It has two other functions as well (BBG 12.7):

When αυτος is in the nominative case and agrees with a noun, then it is an intensive pronoun.

αὐτὸς ὁ ἀνήρ or ὁ ἀνὴρ αὐτός = the man himself

ἀνδρός αὐτοῦ = of the man himself

When αυτος is preceded by the article in any case:

ὁ αὐτός ἀνήρ = the same man

τοῦ αὐτοῦ ἀνδρός = of the same man