2nd Death is the eternal opposite of Eternal life.
Its the continuation of not being born again.
Its "Gods wrath REMAINS On them""". John 3:36, after they die.
1st Death is "adamic".... and when we are born again , that death, that separation from God, ends.
2nd Death, is ... can never change from "adamic" to "Son of God".... so, that separation from God that is the "spiritual 1st Death" of Adam, can't be changed after you die, so that is 2nd Death.... its gone from 1st death, on earth, that can be changed by being born again...to, 2nd Death in eternity, that can't be changed after you die.
2nd means eternal.
final.
unchangeable.
Can never be born again, after you DIE. = 2nd DEATH.
Why?
You can't be born again in hell.
How do you know?'
Because everyone who is in Hell right now, ALL BELIEVE IN JESUS, NOW....... and it does not help them, and will never.
They are in 2nd DEATH, just the beginning, and there is no recovery, it is eternal.