Atonement. Though some take it simply to mean “at-one-ment,” reducing the meaning to simple reconciliation, the idea of the Hebrew word k-ph-r carries the ideas of blotting out sin and satisfying the penal demands of the law. As Leon Morris points out, “Its use in theology is to denote the work of Christ in dealing with the problem posed by the sin of man.” Morris highlights that its use in the NT emphasizes Christ’s death as substitutionary, sacrificial, and expiatory. Reconciliation is possible because one’s sins have been blotted out and their penalty satisfied. Leviticus 17:11, which speaks of atonement being made by the blood of sacrifice is echoed in Hebrews 9:22 which states that the law provides for almost all things to be cleansed with blood and that apart from the shedding of blood nothing will be cleansed.
Expiation/Propitiation. both words express closely related ideas. In propitiation, the emphasis is on the person offended whereas in expiation the emphasis is on the act itself. Both, however, have to do with the blotting out of a sin through a sacrificial act.
Leon Morris says that, “Propitiation properly signifies the removal of wrath by the offering of a gift.” Morris points out that there are more than twenty words used to express the wrath of God as applied to Yahweh in the OT and collectively they are used over 580 times.  The concept of God’s wrath, Morris says, “cannot be eradicated from the Old Testament without irreparable loss.” Many object to this because the idea of an angry God is offensive to them or they refuse to see it in Scripture though Psalm 7:11 says that “God is angry with the wicked every day.” This objection is based on a misunderstanding of “wrath,” which we tend to see as irrational anger and which characterized pagan deities. God’s wrath is not capricious, however, but a consistent, stern reaction to the sinfulness of humanity.
In the NT, the hilaskomai word group is used in Romans 3:25; Heb. 2:17; 1 John 2:2; 4:10 in relation to Christ’s death. In Romans and in Hebrews, the word is used in conjunction with statements about Christ’s blood, using sacrificial language, and Hebrews 2:17 specifically links this act and its resulting propitiation to the sins of the people so that the sins of the people necessitated the act itself.
It is true that Luther rejected of the word “satisfaction” in this regard due to its “association with penance in the Catholic tradition.” Though the “satisfaction” view may have been used to support medieval notions of penance and the Mass as outworkings of the idea of the necessity of a payment in the form of blood and suffering, but such medieval ideas represent perversions of the Scriptural view.
Redemption. “Redemption” has to do with freeing someone based on the payment of a price. While this has often been used to support the ransom theory of the atonement, it does not. The word translated “redemption” is apolytrōsis and though this word is not common in extrabiblical Greek, used only eight times, this word is found ten times in the Greek NT. Leon Morris notes that the emphasis in this word is on the cost of redemption and it is linked to the death of the Savior. For example, in Ephesians 1:7 and Romans 3:24f where it is stated that the cost of redemption is Christ’s blood and in Hebrews 9:15 the cost is Christ’s death. Twice in 1 Corinthians Paul stresses the cost (6:19f. and 7:22f.) without naming what the cost was though Galatians 3:13 and Mark 10:45 both carry the substitutionary idea.
Morris points out that the NT writers could very well have used another word, rhyomai, which means “to rescue” had they only wanted to stress the idea of deliverance. That they chose this relatively rare word indicates that they intended to stress the idea of the cost paid for the deliverance, namely, the death of the Son.
 A. A. Hodge, The Atonement (Grand Rapids: Baker, 1907), 33.
 Hodge, 34.
 D. R. W. Wood and I. Howard Marshall, New Bible Dictionary, 3rd ed. (Leicester, England; Downers Grove, Ill.: InterVarsity Press, 1996), 102.
 D. R. W. Wood and I. Howard Marshall, New Bible Dictionary, 3rd ed. (Leicester, England; Downers Grove, Ill.: InterVarsity Press, 1996), 975.
 Leon Morris, The Apostolic Preaching of the Cross (Grand Rapids: Eerdmans, 1976), 131.
 Morris, Cross, 156.
 Morris, Cross, 131.
 Morris, Cross, 37.