In the card game contract bridge, a forcing bid is any call that obliges the partner to bid over an intermediate opposing pass.
Owing to the partnership's bidding system or a bridge convention, partner must "keep the bidding open",[1] i.e. not pass, thereby preventing his left-hand opponent from ending the auction with a pass and enabling the "forcing bidder" to bid further.
Also, introducing a new suit at three level is generally treated as forcing provided this bid is made in a non-limited hand.
The main reason it is necessary to have certain bids in the system designated as forcing is to allow the partnership to start a dialogue exploring for the right contract.
This is no easy territory, as is exemplified by the fact that in certain auctions even a pass can be forcing.