mia

Mia is simply mi with the adjective ending -a, and it then behaves like any other adjective: it agrees with its noun in number and case, giving mia mano, miaj manoj, mian manon, miajn manojn. Every pronoun builds its possessive the same way, so once you have mia you also have via, lia, ŝia, ĝia, nia and ilia for free. Because it is a real adjective, it can stand on its own as "mine": ĝi estas mia.