Stayman Convention

A response of 2C after a 1NT opening, or 3C after a 2NT opening is asking Opener for 4 card Majors.

Opener's rebids after 1NT to 2C	Responder's rebids
2D with no 4 card major	2H or 2S: a weak takeout 3H or 3S: invitational, but not forcing 2NT: 11 - 12 3NT: 13 - 15 3C: a weak hand with long clubs 3D: asks opener to show best major
2H or 2S with a 4 card major (with both bid 2H)	Pass on a weak hand with a fit 2S (over 2H) 3H or 3S: Invitational, but not forcing 4H or 4S 2NT: 11 - 12 3NT: 13 - 15

After 2NT to 3C:  responses are similar at one level higher