The English word "convert" originated from a compound Latin word, con, meaning to, and verto, meaning turn (verto is found in other English words, such as inverse, which means to turn inward, and reverse, which means to turn back). Convert means to turn in another direction, and, or, and then, to change form.
"Covert" (as a noun or adjective) or "converted" are used to translate a number of Hebrew and Greek words. In the Old Testament, the Hebrew word pronounced shoob means to turn (i.e. the same meaning as the English word), but more specifically, to turn from a wrong direction back to the right direction. The other Hebrew word is pronounced haw-fawk; it means to turn over (similar in meaning to the English expression "to turn over a new leaf").
In the New Testament, the Greek word pronounced ep-ee-stref-oh means to come back (similar in meaning to the above Hebrew word that means to turn from a wrong direction back to the right direction). The other Greek word (the one most-used in the New Testament) is pronounced stref-oh; it means to turn around, and in doing so, to be strengthened at the base, or to have a stronger place to stand.
"Repent ye therefore, and be converted, that your sins may be blotted out"
Many people think of conversion as a "New Testament" act, but it's also found far back in Bible History (e.g. Abraham was converted from a family of idol worshippers to an obedient man of the LORD - see Circumcision). The statement "Then will I teach transgressors thy ways; and sinners shall be converted unto thee" is found in the "Old" Testament.
"51:7 Purge me with hyssop, and I shall be clean: wash me, and I shall be whiter than snow. 51:8 Make me to hear joy and gladness; that the bones which thou hast broken may rejoice. 51:9 Hide thy face from my sins, and blot out all mine iniquities. 51:10 Create in me a clean heart, O God; and renew a right spirit within me [see The Cure For The Carnal Mind]. 51:11 Cast me not away from thy presence; and take not thy holy spirit from me. 51:12 Restore unto me the joy of thy salvation; and uphold me with thy free spirit.
Conversion begins (after and with the coming of the Holy Spirit - again, see The Cure For The Carnal Mind) with the turning away from human arrogance, which is in fact Satanic arrogance (if you want to know what Satan looks and sounds like, just glance at any arrogant, loud-mouth human hypocrite).
"18:1 At the same time came the disciples unto Jesus, saying, Who is the greatest in the kingdom of heaven?
Without repentance, there is no conversion.
"3:19 Repent ye therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord; 3:20 And he shall send Jesus Christ, which before was preached unto you: 3:21 Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began." (Acts 3:19-21 KJV)
And then, without conversion, there is no salvation, "he which converteth the sinner from the error of his way shall save a soul from death."
"5:13 Is any among you afflicted? let him pray. Is any merry? let him sing psalms. 5:14 Is any sick among you? let him call for the elders of the church; and let them pray over him, anointing him with oil in the name of the Lord: 5:15 And the prayer of faith shall save the sick, and the Lord shall raise him up; and if he have committed sins, they shall be forgiven him. 5:16 Confess your faults one to another, and pray one for another, that ye may be healed. The effectual fervent prayer of a righteous man availeth much.
Fact Finder: What is the "soul"? Is the soul physical or spirit?