The article the is declined masculine, feminine, and neuter like the nouns, thus—

τὸ
τὸν  τὴν  τὸ

It never has α in the feminine.

The verb to be, εἰμί, has second person εἶ, third ἐστί, or before a vowel ἐστίν, and in plural ἐσμέν, ἐστέ, εἰσί.

The pronouns of the first and second persons are—

ἐγώ  μοῦ, ἐμοῦ  μοῖ, ἐμοί  μέ, ἐμέ
Iof meto me me
σύσοῦσοίσέ
thouof theeto theethee

λαμπρός ἐστι ὁ ἥλιος,  the sun is bright.

καὶ καλὴ ἡ ἡμέρα,  and the day beautiful.

ὁρᾷς τὸν ἥλιον;  do you see the sun?