The English translation of "regeneration" is derived from 2 Greek word groups: "gennaō" and "palingenesia."

The Greek word group "gennaō" is used frequently in the New Testament usually in the literal sense and at times in the figurative. In the context of salvation, "gennaō" means "born" or "birth" as in "to receive a new origin."

There was the true Light which, coming into the world, enlightens every man. He was in the world, and the world was made through Him, and the world did not know Him. He came to His own, and those who were His own did not receive Him. But as many as received Him, to them He gave the right to become children of God, even to those who believe in His name, who were born (gennaō), not of blood nor of the will of the flesh nor of the will of man, but of God. (John 1:9-13)

In alluding to the Jews rejection of Jesus, John indicates that the "children of God" are not of a natural physical descent. Regarded as "sons of Abraham," Jews could not assume they were "children of God" by covenant either.

Only those who believe in Jesus receive the right of being born of God; the emphasis is on a spiritual relationship by receiving a new origin of birth.

Now there was a man of the Pharisees, named Nicodemus, a ruler of the Jews; this man came to Jesus by night and said to Him, "Rabbi, we know that You have come from God as a teacher; for no one can do these signs that You do unless God is with him." Jesus answered and said to him, "Truly, truly, I say to you, unless one is born (gennaō) again he cannot see the kingdom of God." Nicodemus said to Him, "How can a man be born (gennaō) when he is old? He cannot enter a second time into his mother's womb and be born (gennaō), can he?" Jesus answered, "Truly, truly, I say to you, unless one is born (gennaō) of water and the Spirit he cannot enter into the kingdom of God. That which is born (gennaō) of the flesh is flesh, and that which is born (gennaō) of the Spirit is spirit. Do not be amazed that I said to you, ‘You must be born (gennaō) again.' The wind blows where it wishes and you hear the sound of it, but do not know where it comes from and where it is going; so is everyone who is born (gennaō) of the Spirit." (John 3:1-8)

In speaking of being "born again," Jesus alludes to several implications:

Jesus is emphasizing the spiritual condition of a human being.

To Jewish teacher's question of "how can a person be reborn," Jesus indicates that the answer has its basis in the Old Testament; it was based on Ezekiel's prophecy of the New Covenant.

Then I will sprinkle clean water on you, and you will be clean; I will cleanse you from all your filthiness and from all your idols. Moreover, I will give you a new heart and put a new spirit within you; and I will remove the heart of stone from your flesh and give you a heart of flesh. I will put My Spirit within you and cause you to walk in My statutes, and you will be careful to observe My ordinances. You will live in the land that I gave to your forefathers; so you will be My people, and I will be your God. (Ezek 36:25-28)

Only the Believer who has been born of the Spirit will see the Kingdom of God. A Believer's true existence is not of this world, it is in the Kingdom of God through Jesus Christ.

Despite being a recognized teacher of the Law, Nicodemus had difficulty understanding the abstract idea of being "born again."

"Palingenesia" is a compound noun from "palin" (which means "again") and "genesis" (which means "birth" or "origin"). It is used only twice in the New Testament.

But when the kindness of God our Savior and His love for mankind appeared, He saved us, not on the basis of deeds which we have done in righteousness, but according to His mercy, by the washing of regeneration (palingenesia) and renewing by the Holy Spirit, whom He poured out upon us richly through Jesus Christ our Savior, so that being justified by His grace we would be made heirs according to the hope of eternal life. (Tit 3:4-7)

Similar to Jesus' conversation to Nicodemus alluding to the New Covenant, the apostle Paul here speaks of "regeneration" as the act of God through the renewing and restorative power of the Holy Spirit. Its context is reminiscent of the psalmist prayer, "create in me a clean heart, O God, and put a new and right spirit within me" (Ps 51:10). Paul envisions a "washing" of the heart and "installing" a new spirit within the Believer.

Then Peter said to Him, "Behold, we have left everything and followed You; what then will there be for us?" And Jesus said to them, "Truly I say to you, that you who have followed Me, in the regeneration (palingenesia) when the Son of Man will sit on His glorious throne, you also shall sit upon twelve thrones, judging the twelve tribes of Israel. And everyone who has left houses or brothers or sisters or father or mother or children or farms for My name's sake, will receive many times as much, and will inherit eternal life. But many who are first will be last; and the last, first. (Matt 19:27-30)

In this passage, Jesus speaks of "regeneration" in the context of the renewal of the world in the end time (Rev 21:1-5) where life as a Believer will be vastly different.

There is an impression that regeneration isn't completed until the very end when Believers are resurrected for eternal life. While the Bible is silent on this, the logic does make sense.

Regeneration and its associated figures of speech highlight the contrasting reality of a human being's natural state as being spiritually dead (1 Cor 2:14), children of wrath (Eph 2:1-3), and walking in darkness (John 3:18-20; Eph 5:6-8).

"Born again" regards Believers as passive recipients of the active work of the Holy Spirit (John 3:8) and occurs instantly at initial salvation (1 Pet 1:23-25; James 1:18). It signals a change in the origin of birth.

"New creation" signals the transformative effects of regeneration and perhaps going beyond one's spiritual state (2 Cor 5:17). It includes a transformation of the one's ethics and lifestyle (Eph 4:17-24).

"Children of God" is the direct result of being "born of God" and entitles Believers to a birthright as inheritors of God's promise (Gal 4:1-7).