"die" は動詞、"dead"は形容詞。
変化形 : dies , dying , died / 《複》dice , 《複》dies
dieの方の例文：
"This tree died this year, because of the pollution"
"Her father died five years ago.
*agoが来ているので過去形でOK。
"It is five years since her father died"
deadの方の例文：
"This dead tree is going to be used as firewood soon"
"Her father has been dead for five years"
