That repentance can be defined as a change of mind should be obvious, but that is about the most basic and anemic definition possible. It is possible one can have regret or remorse without changing his mind, but a change of mind is the very essence of a turning in one's heart or soul. A change of mind could be understood as a turning of the mind or heart.
The important point to remember, however, is repentance is much more than a basic change of mind. The Bible speaks of people "chang[ing]" their "mind" using those very terms (Hab 1:11; Acts 28:6) and also refers to it implicitly in Eze 23:17, 18, 22; Luke 8:35; Rom 12:2, 16; 1Cor 1:10; 2Cor 13:11; Eph 4:23; Phil 1:27, 2:2, 5; Heb 8:10; 1Pet 3:8, 4:1, etc., but it does not equate a simple mind change with repentance. Paul speaks about people changing (renewing, etc.) their minds and also about "repentance" and does not confuse the two. The terms are not synonymous. Only someone with an agenda would claim they are.
The King James translators even said in their marginal notes an alternate translation instead of "repentance" in Heb 12:17 is "change his mind." Such a statement would be silly and redundant if they thought the terms were synonymous. They knew repentance means more than just a mind change.
As we mentioned, some who hold the "free grace" position insist a Bible reader should substitute "change [his] mind" every time he sees "repentance" in the Bible, but this would remove authority, intent, and power from most passages. "Change my mind" would dilute them significantly.
Anyway, if the King James translators wanted to use "change your mind" in place of "repentance" they very easily could have done so, but the providence of God led them (and practically all other translations as well) to use a form or "repent" instead because the term carries more meaning and weight.
It is our our contention that nearly every use of repentance found in the Scriptures reflects all three of the heretofore mentioned meanings to proportional degree. With some usages regret or remorse is most emphasized with a turning and change of mind not very obvious. With others just the opposite is true. A change of attitude is the principle thought while regret and sorrow are barely seen. As always, context is the determining factor.
Some like to define repentance as "a change of mind that results in a change of action." Although it is not a complete definition it will work if the "action" is believing on Christ and not an outward change of life. True evangelical repentance will always result in the faith action of believing the gospel when it is presented (see details below). However, if the action must be some sort of change in the person's life, like giving up a vice, baptism, or going to church, then works are being mingled with the repentance.
Repentance and "works meet (fitting) for repentance" (Acts 26:20) are not the same. The regret and turning of mind is the actual repentance; the mental and spiritual action of believing on and receiving Christ is its paramount fruit. After one becomes a believer, his life should be marked by works or fruit indicating his belief. His daily life should reflect what he professes to believe, but fruit has no bearing at the moment one believes.
Evangelical repentance in itself is not an act that should change a person's outward or visible life. Faith and thanksgiving should be the motivators for a believer to do right and live for God (Rom 12:1-2). The role of evangelical or salvational repentance is to get one to faith, not to get him give up sin or live a "better" life.
Dear reader, please understand we are speaking here of evangelical or salvational repentance. The single purpose of this repentance is to prepare one's heart to have faith in Christ's salvation. After one is saved repentance should still be a part of his Christian life, but its purpose is no longer to get him saved or keep him saved. Its purpose is to lead him to a more holy life day by day.
The danger of evangelical repentance being tied to good works is faith can easily be skipped! Notice very carefully, if one "repents of his sins," is sorry for them, and then tries to do better, he has fulfilled the "a change of mind that results in a change of action" definition, but he still doesn't have any salvation because belief in Christ has been bypassed. In your author's mind "a change of mind that results in [the action of] faith in Christ" is a much more Scriptural definition.