Herbert Weir Smyth, A Greek Grammar for Colleges

a. The enclitic forms μου, μοι, με; σου, σοι, σε are used when the pronoun is unemphatic, the longer forms ἐμοῦ, ἐμοί, ἐμέ and the accented σοῦ, σοί, σέ are used when the pronoun is emphatic. Thus, δός μοι τὸ βιβλίον give me the book, οὺκ ἐμοί, ἀλλὰ σοὶ ἐπιβουλεύουσι they are plotting not against me, but against you. See 187 a. On the use after prepositions see 187 N. 2.

b. For ἐγώ, ἐμοί, σύ the emphatic ἔγωγε, ἔμοιγε (186 a), σύγε occur. Also ἐμοῦγε, ἐμέγε.

c. The use of the plural you for thou is unknown in Ancient Greek; hence ὑ_μεῖς is used only in addressing more than one person.

d. Of the forms of the third personal pronoun only the datives οἷ and σφίσι (ν) are commonly used in Attic prose, and then only as indirect reflexives (1228). To express the personal pronouns of the third person we find usually: ἐκεῖνος, οὗτος, etc., in the nominative (1194), and the oblique forms of αὐτός in all other cases.

e. For the accus. of οὗ the tragic poets use νιν (encl.) and σφε (encl.) for masc. and fem., both sing. and pl. (= eum, eam; eos, eas). Doric so uses νιν. σφίν is rarely singular (ei) in tragedy.

f. ἡμῶν, ἡμῖν, ἡμᾶς, ὑ_μῶν, ὑ_μῖν, ὑ_μᾶς, when unemphatic, are sometimes accented in poetry on the penult, and -ι_ν and -α_ς are usually shortened. Thus, ἥμων, ἧμιν, ἧμας, ὕ_μων, ὗμιν, ὗμας. -ι_ν and -α_ς are sometimes shortened even if the pronouns are emphatic, and we have ἡμίν, ἡμάς, ὑ_μίν, ὑ_μάς. σφάς occurs for σφᾶς.