I think that it depends on the conception that a person has about good and bad things, for example, in my case and in my context, homosexuality is a natural and common thing, because I've created based on my own experience my conceptions about the concept, but for some other people it is a sin, because of all that they have been thought... So I think that for me, a sin is something that has nothing to do with my own reality, ideas and expectations of the world.
I guess Sin is subjective and everyone has different views of what they label as Sin but i believe most sane human beings can all agree that murder, rape and such heinous crimes are serious Sins. Personally, if i did something that triggers my conscience, i believe I've sinned. If i feel guilty over something, then I've sinned.
Sin is any thought or action contrary to the will of God. It is pretty clear cut and easy to understand for me. If it is contrary to God's will it is by nature evil.
