campboy, on 2014-September-16, 07:05, said:
I think the crucial word there is "mutual". If one player has experience which leads him to expect it to be takeout, and the other has experience which leads him to expect it to be penalty, that doesn't constitute an understanding.
That is correct, but it cannot be taken literally:
Many years ago I played a casual rubber with a friend who was very competent in systems (definitely class A player), we were not regular partners and agreed to play "Natural".
He suddenly bid 5NT out of the blue sky, we had not discussed this call, but he knew my background and hoped that I would understand it as the "big free 5NT" convention (asking for trump quality) which indeed I did.
Did we have any agreement on this convention? Certainly not.
Had we discussed it in any way? Certainly not.
Did we have a
mutual experience or awareness of this convention?
Absolutely! (Each of us in our own environment.)
What should be my answer if I had been asked about this bid? Of course: "I understand it as asking for my top honours in trump"