What is sin? ( Romans 3 v 20 - 23 )

It is W Barclay who points out  the meaning of the word sin,the first meaning is failure,the second is coming short. It may not be a nice thing to say, but in Gods eyes we are all failures,now what does that mean?,it simply means we have failed to keep Gods law,coming short is saying that we have no matter how much we have tried,we have come short of Gods perfect standard.In Romans 3 v 23 we read that  all have sinned and come short of the glory of God.The standard we are supposed to attain to, is to perfectly keep Gods law,not just outwardly but also inwardly, CP Matthew 5 v 21-22 / 27-28. The law of God is summed up in the following words,                                                                                                                                                                                                                                                                                             Love the Lord your God with all your hearts                                                                                            and with all your soul and with all your mind.                                                                                         This is the first and greatest commandment.                                                                                             The second is like it,' Love your neighbour as                                                                                           yourself.                                                                                                                                                                      (  Matthew 22 v  37 - 39 )