In the auction, each player calls in turn, starting from the dealer. There are 4 types of calls:
An action is a call other than pass.
Meaning of calls Edit
Nearly all calls carry a meaning. The agreed meaning of a call must be made known to the opponents when requested.
A few calls do not have a meaning on their own. However, if alternatives are allowed in place of that "meaningless" call, something can be drawn by negative inference. For example, playing 2/1 GF and fourth suit artificial,
- not have 3 ♥s (otherwise, he would have bid 2♥);
- not have 6 ♣s (otherwise, he would have bid 3♣);
- not have 4 ♠s (otherwise, he would have initially responded 1♠);
- not have 4 ♦s (otherwise, he would have raised 2♦ to 3♦),
opener is known not to have 4 ♠s and 17 points at the same time, otherwise, he would have super-accepted.
natural vs. artificialEdit
- A pass is natural if it indicates unwillingness to make any other call.
- A double or redouble is natural if it indicates willingness to increase the score of the contract.
- A bid is natural if it suggests willingness to play in that denomination.
An artificial call is a call which suggest something else other than the call itself, even with no relationship to the call itself at all:
- An artificial pass may indicate a strong hand (Strong pass system), or when an convention has been interrupted, a response (see DOPI).
- An artificial double may be used as a request to lead the double suit (Lead directing double).
- An artificial redouble may be used to rescue the partnership from a bad doubled contract (SOS redouble).
- An artificial bid may be used to initiate or respond a convention.
However, as some conventions are so widespread, they may be treated as natural in a natural bidding system, for example, as the need for penalising a low level contract is so little, a double at low level is treated as takeout, even at the natural sense.
forcing vs. non-forcingEdit
Main article: Forcing
A forcing call is a call which requires partner to bid if the opponent in-between passes. A non-forcing call is a call which may be passed. There exists an intermediate type, called semi-forcing, which requires partner to bid unless he has a very specific kind of hand which should be passed, as part of the agreement.
The degree which a call urges the partner to bid are order as follows: