Do you know the English expression “break a leg”? It sounds a little strange, but it means “good luck”! People say it to actors or performers before they go on stage. The origins of this expression are not known, and there are many different ideas.
In the world of theatre, it is believed that wishing someone “good luck” is actually “bad luck”. This is a superstition. There are many superstitions in the theatre. You can read more about them here.
So if your friend is going to appear in a play or in a concert on stage, don’t forget to tell them to break a leg!