The Biblical definition of sin is very different to the ideas that many have that confines sin to merely bad things that a person does, like lying stealing, sexual sin or murder.
The topic of sin is not a popular one today. Many view the concept of sin as archaic and demeaning -- something that needs to be cast aside in light of current ' modern thought'. Christians however know that there are some things taught in God's Word which will never become outdated. Sin is one such topic that is as relevant today as it was two thousand years ago.
The world view is that the individual or in some cases, society decides what is right or wrong. But one persons conscience differs from the next person and what a society or culture accepts differs with the passing of time. In the time of Rome leaving babies out to die of exposure was accepted and as the world was Christianized it became not just sin but a crime, however nowadays in many countries killing your unwanted baby before birth is not only accepted but encouraged.