What is sin?

What is sin? I think everyone knows, so why bother making it sound less evil or make it PC? It is what it is and we all know it. The sinner, who after all was a woman as well as a sinner (Luke 7:36, 37 ff) dared to go and see Christ at the Pharisee's house, where the Pharisees were all together at a feast - Nicodemus (John 3:2), who regarded himself as a righteous man, dared go to him only at night.