αὐτός follows the pattern, in the masculine, of the masculine —ος family of nouns. In the feminine, it follows the pattern of the feminine —η family of nouns.
So depending on the gender and number suffix, αὐτός can be translated as he, she, him, her, himself, herself, they or them, as appropriate in the context.
Masculine
Feminine
Singular
Plural
Singular
Plural
Nominative
αὐτός
αὐτοί
αὐτή
αὐταί
Genitive
αὐτοῦ
αὐτῶν
αὐτῆς
αὐτῶν
Dative
αὐτῷ
αὐτοῖς
αὐτῇ
αὐταῖς
Accusative
αὐτόν
αὐτούς
αὐτήν
αὐτάς
Now it is time to get back to Acts 1:6.Unpacking all the possible endings of αὐτὸν has been a rabbit trail...but a pretty important rabbit trail. Since αὐτός is an important, enormously common word on its own, and since it shares suffixes with two classes of nouns in all four cases, it is a good word to get a handle on.