Sin means to miss the mark.
This word was used in archery, when the target was missed. It would seem clear, therefore, that we cannot understand the idea of sin in the right way unless we gain some idea of what it is we have to aim at.
To miss the mark is “sin”; but what is the mark?
The transformation of a man can be thought of as The Mark to be aimed at.
The Mark is to conform “to the image of his Son”.