αυτος is usually the third person, personal pronoun.
Singular:
| Singular | |||
| Masculine | Feminine | Neuter | |
| Nominative | αυτος | αυτη | αυτο | 
| Genitive | αυτου | αυτης | αυτου | 
| Dative | αυτω | αυτη | αυτω | 
| Accusative | αυτον | αυτην | αυτο | 
Plural:
| 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):
αυτος as an intensive pronoun:
 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
