stayman convention
Stayman is a bidding convention used by a partnership to find a 4-4 or 5-3 trump fit in a major suit after making a one notrump 1NT or opening bid; it has been adapted for use after a 2NT opening as well.
After an opening bid or an overcall of 1NT (2NT), responder or advancer bids an artificial bid of 2♣ ( or 3♣ after a 2NT opening) to ask opener if they hold a four card major suit.
The club bid which is artificial typically promises four cards in at least one of the major suits and enough strength to continue bidding after partner’s response (8 HCP for an invitational bid opposite a standard strong 1NT opening or overcall showing 15-17 HCP, 11 HCP opposite a weak notrump of 12-14 HCP, or 5 HCP to go to game opposite a standard 2NT showing 20-22 points).
It also promises distribution that is not 4333.
The opener replies with the following rebids:
2♦ (or after 2NT- 3♦) denies four or more cards in either major suit.
2♥ (or after 2NT – 3♥) shows at least four hearts (also meeting the criteria for an honor holding as may be set by partnership agreement). 2♠ (or after 2NT – 3♠) shows at least four spades.