Sin is the transgression of God's law. It has a broad application in that sin can be defined as all unrighteousness, missing the mark or falling short of the character of God. Whatever is not of faith is sin, and when a person knows to do good but does not do it, it is sin. The penalty for sin is death in the Lake of Fire. Unpardonable sin is the willful, knowledgeable and continued transgression of the commandments of God. It also includes the willful rejection of God's salvation and blasphemy of the Holy Spirit, which is despising the works God does by the power of His Spirit and attributing them to Satan. These sins are unpardonable because the person will not repent. All sins can be forgiven by God's mercy through the blood of Jesus Christ.

Scripture References:
I John 3:4; 5:17;   Ephesians 2:1;   Romans 14:23;   James 4:17;   Romans 6:23;   Revelation 20:14;   Galatians 5:19-21;   Matthew 12:31;   Hebrews 10:26-29;   I John 1:7, 9;   Romans 8:1-3;