Forgivable sins in the Bible
The New Testament distinguishes among sins in various contexts.

In 1 John, the author distinguishes between two types of sin (1 John 5:16-17). One class of sin leads to the loss of eternal life, but eternal life can be regained if a fellow Christian prays that the sinner be forgiven. The other class of sin leads to death, and the Christian is not instructed to pray that a fellow Christian be forgiven for such a sin. Since either class of sin puts one’s eternal life in jeopardy, both would fall in the category of mortal sin.

The New Testament also mentions the unforgivable sin, blasphemy against the Holy Spirit (Mark 3:28-29).

The New Testament does not refer to a class of sins that leads to punishment other than death (venial sins).