One of the most famous scripture verses from the Bible is John 3:16, which is a succinct description of God's love toward us, which leads to our salvation from sin unto new life.
For God so loved the world, that he gave his one and only Son, that whoever believes in him should not perish, but have eternal life. (John 3:16)
While most often the focus is on the "eternal life" part of the promise, much can be learned from the phrase "shall not perish."
That base word for "perish" (αποολλυμι) can mean several things, all related: to destroy; to put out of the way entirely or abolish or ruin; to render useless or to kill; to declare one to be put to death; to lose or be lost.
The verb comes from the preposition απο, indicating separation of a part from the whole, and the noun ολεθρος (Olethros), which means ruin, destruction, or death. It was the Greek god of such things, closely related to Moros, the god of destiny, fate or doom.
Together one can see how the common definition for the whole word, "to perish, be lost, to ruin or destroy," embodies the two parts; it is a destruction or ruin unto separation. Not just doom, but to the degree that it separates the thing from its previous surroundings, etc. It is a thorough destruction or abolishing, because it ruins the thing to a complete separation.
The Savior & Finder vs. the Destroyer & Thief
The thief only comes to steal, kill, and destroy. I came that they may have life, and may have it abundantly. (John 10:10)
This word is used many times in the New Covenant, which can give us insight into from what the Son of God has truly saved us. When God sent His Son that we might "not perish" but rather have eternal life, we can come to understand where we were headed before He came.
In addition, we can also learn about that other side of the situation, where we were headed—that there is one who seeks to destroy. He is personified once in Revelation as אבדון (Abaddon) and απολλυων (Apollyon, or Destroyer) (Revelation 9:11), and is seen elsewhere throughout the New Covenant as the Enemy of God and His people.
This entire matter is about us being both lost and found, a deeper look at sin and forgiveness.