αὐτός is a definite adjective and a pronoun. It has three meanings:
a. self: standing by itself in the nominative, αὐτὸς ὁ ἀνήρ or ὁ ἀνὴρ αὐτός
b. him, her, it, them, etc.: standing by itself in an oblique case (never in the nominative). The oblique cases of αὐτός are generally used instead of οὗ, οἷ, ἕ, etc., as ὁ πατὴρ αὐτοῦ
c. same: when it is preceded by the article in any case: ὁ αὐτὸς ἀνήρ
N.—The article and αὐτός may unite by crasis ( cross68 a): αὑτός, αὑτή, ταὐτό or ταὐτόν; ταὐτοῦ, ταὐτῆς; ταὐτῷ, ταὐτῇ, etc. Distinguish αὑτή
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].