If you've ever tried to come up with a definition of "grace" that satisfies the full breadth of Biblical meaning, you've begun to realize what a daunting task it is.
It isn't that the many definitions of "grace" are untrue; it's just that they tend to be inadequate.
"Unmerited favor" is flat and shallow. It rightly strikes the note of the freeness of grace, without which the word is without its own essential meaning, but it only brings us to the right door. It doesn't take us beyond the threshold.
The GRACE acronym of "God's Riches at Christ's Expense" is better, in that it points to the multifaceted abundance of grace ("riches"), and brings in the additional thought that grace, while free to us, is not free to God. We "are justified by his grace as a gift, through the redemption that is in Christ Jesus" (Romans 3:24). Christ secures grace for us by His active and passive obedience. Grace is at the price of His payment of the ransom-price in His blood. What costs us nothing, cost Him everything He could give.
When I designed a way to present the Gospel in a church I pastored, I devised an acronym based on the word:
God is holyIt had its usefulness in sounding essential Biblical truths; but as a definition of grace (which it wasn't intended to be), it stressed initial salvation, which is an incomplete picture.
Righteousness is required
All have sinned
Christ died for sinners
Each must repent and receive Christ by faith
We must see that grace is more than saving in the sense that it doesn't just bring us to the marriage-ceremony and get us wed. That is, our picture of grace is inadequate if we see it only as making it so that "when that roll is called up yonder [we'll] be there." That is the decisional error that (rightly) calls one to commit oneself to Christ, and then (wrongly) leaves out the truth that this begins an eternal, daily, growing, vital relationship.
The error is not in linking grace-alone to salvation; it is in our view of salvation. We rightly oppose the Pelagian/Arminian "daisy" of "He loves me, He loves me not." Genuine, Biblical salvation is not a hope-so, maybe, one-day-in-the-future affair. We can have confidence that we have eternal life now (1 John 5:13). This is because we stand abidingly saved by grace alone through faith alone in Christ alone (Ephesians 2:8-9).
But saved means more than just a category-switch on the books somewhere Out There. It is that, to be sure (Colossians 1:13), but it is also...
...well, it's what Paul says it is in Titus 2:11-14—
For the grace of God has appeared, bringing salvation for all people, 12 training us to renounce ungodliness and worldly passions, and to live self-controlled, upright, and godly lives in the present age, 13 waiting for our blessed hope, the appearing of the glory of our great God and Savior Jesus Christ, 14 who gave himself for us to redeem us from all lawlessness and to purify for himself a people for his own possession who are zealous for good works.There it is, you see. Grace brings salvation, and it then trains us in holiness. For a doctrine of grace even to approach the robust, multifaceted richness of the Biblical concept, it has to live happily with this section. It can't stumble or turn to mumbling "Yes-but"-ing.
Paul says that the grace of God indeed has appeared in Christ and brought salvation — but God's grace did not stop with merely an external, bookkeeping re-categorization. The inspired apostle writes that grace — grace! — actually trains us in holiness. It is our pedagogue (παιδεύουσα, paideuousa) in sanctification, in holy and hopeful living.
So, while he does distinguish the two, the apostle does not divorce saving grace from sanctifying grace. The one is the necessary cause of the other. If our doctrine of grace does not include both truths, it is at best sub-Biblical, and at worst anti-Biblical.
If you asked the apostle how he was saved, he might answer, "By grace" (Ephesians 2:8-9). But equally, were we to inquire as to the source empowering Paul's Christian life and ministry, he would no less answer, "By grace" (Ephesians 2:10; 1 Corinthians 15:10). Grace, to Paul, is not a static accounting term, but a dynamic reality.
This is why it is such a crime that a school of thought should falsely hide itself behind the rich Biblical word grace, while its actual definition boils down to gutless grace. A "grace" that merely technically categorizes one as "saved," while making no necessary resultant impact on one's life and thought, is nothing like what the apostles would recognize as genuine grace. Their God-given and authoritative notion of grace is that of gutsy grace, a grace which atones, redeems, converts, regenerates, sanctifies, empowers, and keeps. To give false license to unregenerate professions and godless living, under that moniker, is a crime of the first magnitude.
God's grace saves and, necessarily and consequentially, sanctifies.
What God has joined together, let no man sunder.