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In the Bible "Hell" is the grave. The Lake of Fire is a symbol in the book of Revelation for the final destruction of sin and its consequences from the earth. Revelation 20:14And death and hell were cast into the lake of fire....
They cannot be the same thing because that would mean that hell is being cast into itself. The fact that an abstract condition, death, is pictured as being cast into the lake of fire clearly shows the symbolic nature of the lake of fire. Hell in this verse is hades and, in a corresponding verse in 1 Corinthians 15:53-55
For this corruptible must put on incorruption, and this mortal must put on immortality. So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory. O death, where is thy sting? O grave, where is thy victory?
The word translated grave in these verses is exactly the same as the word translated hell in Revelation 20:14.