Posted 2012-November-03, 03:59
Bridge logic says that 4♦ must be forcing (whatever else it means). East can not know that 3NT is not making and 4♦ will score better - which would be the only conceivable reason for taking out a game into a part-score. As to what it does mean, that rather depends on what the rest of the auction has shown. In many natural systems, both players have limited their hands - West by the 2NT rebid, East by the 3♣ rebid. In such a case, 4♦ probably means that East has misbid - either on this round or a previous one! However, if the auction was GF by agreement (eg because 2♣ response is played as GF bid, or the 2NT rebid shows extras), then I imagine East is showing 3 card ♦ support and some sort of slam potential.