Here is what Strong's translation of the word and meaning is. It is the most comprehensive term for moral obliquity. Satan, as Lucifer, had not fallen or been cast out of heaven, because he could not sin without Adam. The only disobedience Lucifer could have done at the beginning was to tempt Adam, and that would show what was in his heart. The action is the result of the thought, but until the action happens there is a chance to cast down the thought and avoid the sin.
Sin is a power, a perversion of good.
Sin is a powerful force, it took the only anointed angel down, and it brought man down as well. It is like matches, used in the right hands they are a useful tool, but in the wrong hands they are dangerous. We do not let children play with matches, but they are around and if the child really wants to play with them and be disobedient then they will get them and play with them. The result is usually a disaster, it can even be fatal. Adam was a child that God had told not to eat the fruit of the tree of knowledge of good and evil.