Because it is associated with "election" and "foreknowledge", the definition for the term "predestine" has been confusing and challenging to understand. Some understand "predestine" as synonymous to "foreknow". To begin the process of clarification, the relationship of these three terms can be seen in the following two verses:

To those who reside as aliens, scattered throughout Pontus, Galatia, Cappadocia, Asia, and Bithynia, who are chosen according to the foreknowledge of God the Father, by the sanctifying work of the Spirit, to obey Jesus Christ and be sprinkled with His blood: May grace and peace be yours in the fullest measure (1 Pet 1:1-2).

For those whom He foreknew, He also predestined to become conformed to the image of His Son, so that He would be the firstborn among many brethren; (Rom 8:29)

These examples establish the fact that God elects and predestines based on His foreknowledge; foreknowledge governs God's elective work.

The verb "predestine" comes from the Greek term "prohorizō," which is the compound of "pro" and "horizō." Grammatically, the verb "prohorizō" is used in the aorist tense which indicates a definite event that will occur at some future time. The active voice portrays God as initiating this action.

"Pro" means "in front" in a spatial sense or "before" in a temporal sense.

"Horizō" means "to determine or ordain" or "to appoint."

Combined as "prohorizō," the meaning of "decide upon beforehand, foreordain" or "pre-appoint" is derived. Through the influence of Jerome, who is largely responsible for the Latin Vulgate, "prohorizō" developed a sense of "destiny" which led to the English translation of "predestine."

The Greek verb "prohorizō" is very rare and is not even found in the Septuagint (Greek Old Testament).

Found once in classical Greek literature by Demosthenes, before the New Testament, "prohorizō" is used to mean "lay claim" in a contractual dispute of property and money. Other extrabiblical uses include the idea of laying claim of a day as in "appointing" a day for a wedding before it occurred.

More detailed studies of "horizō" indicate its original meaning as "setting a boundary" as seen in the Old Testament (Num 34:6; Josh 13:27; 15:12; 18:20). Its cognate compound "aphorizō" provides the Hebrew meaning "to separate" (Gen 10:5; Deut 4:41; Lev 13:4) and when referring to the gospel, it means "to mark or appoint one for God's service" (Acts 13:2; Rom 1:1; Gal 1:15).

From these linguistic studies, instead of "predestine," "prohorizō" is more accurately understood as "pre-appoint" or "determine beforehand." Thus, foreknowledge governs God's elective work and pre-appointment / predetermination.

With a better understanding of "prohorizō," one gains a more accurate understanding of its use in the New Testament (Acts 4:28; Rom 8:29-30; Eph 1:3-12).

"do what your power and plan had already determined beforehand should happen." (Acts 4:28 [Complete Jewish Bible])

In Acts 4:25-26, quoting from Psalm 2:1-2, the apostles understood the opposition to Christ as a fulfillment of this Messianic prophecy. The characters of this Old Testament prophecy were identified as contemporaries of the apostles: "Nations" as Gentiles, "peoples" as people of Israel, "kings" as Herod and "rulers" as Pontius Pilate. Since this prophecy occurred a thousand years before the time of Christ, the apostles saw its fulfillment as evidence of God's sovereign power and will; divine prophecy revealed what was predetermined to occur at its appointed time.

It is worthwhile to note that the events that God "determined beforehand" did not simply involve Believers; it included non-Believers who played an important role in the events leading up to the Crucifixion. The use of "determined beforehand" describes the certainty of God's sequence of election, timing and outcome.

"Furthermore, we know that God causes everything to work together for the good of those who love God and are called in accordance with His purpose; because those whom He knew in advance, He also determined in advance would be conformed to the pattern of His Son, so that He might be the firstborn among many brothers; and those whom He thus determined in advance, He also called; and those whom He called, He also caused to be considered righteous; and those whom He caused to be considered righteous He also glorified!" (Rom 8:28-30 [Complete Jewish Bible])

And we know that God causes all things to work together for good to those who love God, to those who are called according to His purpose. For those whom He foreknew, He also predestined to become conformed to the image of His Son, so that He would be the firstborn among many brethren; and these whom He predestined, He also called; and these whom He called, He also justified; and these whom He justified, He also glorified. (Rom 8:28-30, NASB)

In Romans 8:29 Paul reveals the certainty of complete sanctification by revealing the process of being made holy. By divine foreknowledge and choice, a Believer is predetermined to become like Jesus Christ: justified and glorified. While Paul does not mention faith here, the whole context of Romans is about justification by one's personal decision of faith alone (Rom 3:21-31; 4:1-25; 5:1-21) and sanctification by one's personal faith (Rom 6:1-23; 7:1-25; 8:1-39). Paul states this clearly in his letter to the Galatians:

Even so Abraham believed God, and it was reckoned to him as righteousness. Therefore, be sure that it is those who are of faith who are sons of Abraham. The Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, "All the nations will be blessed in you." So then those who are of faith are blessed with Abraham, the believer. (Gal 3:6-9)

Romans 8:29-30 is difficult to understand as there is considerable confusion with God's divine acts of calling and election. So it is imperative to understand what God committed Himself to do.

1. God chose to be God to Abraham and to his descendants. In the context of salvation, God does not ever say He chooses who Abraham’s descendants will be.

"I will establish My covenant between Me and you and your descendants after you throughout their generations for an everlasting covenant, to be God to you and to your descendants after you. I will give to you and to your descendants after you, the land of your sojournings, all the land of Canaan, for an everlasting possession; and I will be their God." (Gen 17:7-8)

2. To be of God's possession and kingdom of priests, one must have faith: a belief that God is real engendering a trust and obedience to His word.

"'You yourselves have seen what I did to the Egyptians, and how I bore you on eagles' wings, and brought you to Myself. Now then, if you will indeed obey My voice and keep My covenant, then you shall be My own possession among all the peoples, for all the earth is Mine; and you shall be to Me a kingdom of priests and a holy nation.' These are the words that you shall speak to the sons of Israel." (Ex 19:4-6)

3. In Jesus' Parable of the Wedding Banquet (Matt 22:1-14), a parable about salvation, Jesus uses the word "call" in the context of "to invite." In His conclusion, "for many are called, but few are chosen," Jesus indicates that many are invited to come to faith, but the few that do are the ones God chooses to be their God.

Blessed be the God and Father of our Lord Jesus Christ, who has blessed us with every spiritual blessing in the heavenly places in Christ, just as He chose us in Him before the foundation of the world, that we would be holy and blameless before Him. In love He predestined us to adoption as sons through Jesus Christ to Himself, according to the kind intention of His will, to the praise of the glory of His grace, which He freely bestowed on us in the Beloved. In Him we have redemption through His blood, the forgiveness of our trespasses, according to the riches of His grace which He lavished on us. In all wisdom and insight He made known to us the mystery of His will, according to His kind intention which He purposed in Him with a view to an administration suitable to the fullness of the times, that is, the summing up of all things in Christ, things in the heavens and things on the earth. In Him also we have obtained an inheritance, having been predestined according to His purpose who works all things after the counsel of His will, to the end that we who were the first to hope in Christ would be to the praise of His glory (Eph 1:3-12).

In his letter to the Ephesians, Paul affirms the blessing of being a Believer regardless of ethnicity (Jew or Gentile). Believers are pre-appointed to adoption as God's sons. And because of Christ, Believers have received an inheritance which was already predetermined according to God's plan and purpose for Believers.

"Just as He chose us in Him before the foundation of the world" exemplifies the many blessings bestowed on the Believer. That God would choose to be God of Abraham’s descendants "before the foundation of the world" illustrates the magnanimity of God's blessings.

When Paul speaks of "prohorizō," he writes within the context of his personal conversion experience (see Examining the Election, Call and Conversion of Saul the Pharisee). He sees faith as a matter of obedience and his rigorous training as a Pharisee as preparation to be an authentic witness of Jesus Christ.

Paul uses the Greek verb "prohorizō" to demonstrate God's sovereignty and foreknowledge and provides a hope to Believers about their future.

In accordance to God's foreknowledge, often revealed in prophecy, God elects and pre-appoints / predetermines people, nations and events for various roles according to His unfolding plan of salvation through Jesus Christ.

And the God's plan is not yet complete until the Kingdom of God arrives and consummates the adoption of His holy people as His children.

For those who have faith, God will make them His own possession and predestines them to be a kingdom of priests and holy nation (Ex 19:4-6).

For those who believe and place their trust in the resurrection and life of Jesus Christ, God predestines them to an everlasting life (John 11:22-27).

For those who do not believe in the above, God predestines them to a place where sin is removed from His presence (Rev 21:1-8).

Then I saw a new heaven and a new earth; for the first heaven and the first earth passed away, and there is no longer any sea. And I saw the holy city, new Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband. And I heard a loud voice from the throne, saying, "Behold, the tabernacle of God is among the people, and He will dwell among them, and they shall be His people, and God Himself will be among them, and He will wipe away every tear from their eyes; and there will no longer be any death; there will no longer be any mourning, or crying, or pain; the first things have passed away."
And He who sits on the throne said, "Behold, I am making all things new." And He said, "Write, for these words are faithful and true." Then He said to me, "It is done. I am the Alpha and the Omega, the beginning and the end. I will give water to the one who thirsts from the spring of the water of life, without cost. The one who overcomes will inherit these things, and I will be his God and he will be My son. But for the cowardly, and unbelieving, and abominable, and murderers, and sexually immoral persons, and sorcerers, and idolaters, and all liars, their part will be in the lake that burns with fire and brimstone, which is the second death." (Rev 21:1-8).