No harm no foul
‘No harm no foul’ means ‘It’s not a big problem’. More fully, it means ‘You broke a rule, but we will not punish you because you didn’t cause damage or hurt (harm)’. This expression comes from American basketball. In American basketball a referee should not stop the game unless the mistake hurts someone or will change the game results. So we use this expression when someone makes a mistake, but the mistake didn’t hurt or damage anyone.
A: Sorry I’m late. I forgot my bag. I had to walk all the way back home to get it.
B: Well, there’re no important meetings this morning so it’s okay. No harm no foul.
A: Your neighbor used your parking spot while you were on vacation.
B: Really? Well, I wasn’t using it anyway. No harm no foul.
Would you say ‘No harm no foul’ if your neighbour used your parking spot? Or would you be angry?