Revelation 20:14; The Second Death
Revelation 20:14 (KJV) And death and hell were cast into the lake of fire. This is the second death.
The lake of fire is the same as the second death according to the words – “… the lake of fire. This is the second death. “
The last words of Revelation 21:8 make the same equation.
Revelation 21:8 (KJV) But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death.
As a second and higher life exists for the righteous, a second and deeper death awaits the wicked (cf. Revelation 2:11; 20:6) (Alford).
Revelation 2:11 (KJV) He that hath an ear, let him hear what the Spirit saith unto the churches; He that overcometh shall not be hurt of the second death.
Revelation 20:6 (KJV) Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years.
In the new order, the lake of fire is the nearest analogue of death in the present creation (Swete). The lake of fire is a figure of speech to accommodate a limited human understanding of what eternal punishment will be, but it nevertheless corresponds to reality. Just as the rich man in hell experienced unbearable torment in flames (Luke 16:23-24), those in the lake of fire will have to endure punishment of the same nature. No significance difference separates the physical and the spiritual reality embodied in the lake-of-fire terminology (Walvoord). Its unending torment makes “the second death” a suitable title for it.
[Robert L. Thomas, Revelation. 8-22 – An Exegetical Commentary, Moody, 1995, 434]