New Minor Forcing

..1C - 1S - 1NT - 2D ( NMF)

2D is artificial, showing 11+ points and asking Opener to further describe his hand. Responder is interested in game, usually has a five-card major and is looking for a 3 card fit

Opener's responses to 1C-1S-1NT-2D , in order of priority, are:

Obviously if the bidding goes 1C-1H-1NT-2D then opener has denied 4S so Responder is only looking for Heart support.

Because first response to New Minor Forcing is to show 4H if you have them , a 2H bid by Responder instead of NMF shows either 5-5 or 5-4 Spades and Hearts (too weak to bid NMF ) Also if Responder bids 3H instead of using NMF then he is 5-5 at least and has 11 HCP or more.

New Minor Forcing is OFF in competition.

If Openers third bid was 2H Responder still doesnt know if opener has 3 card Spade support so a rebid by Responder of 2S is forcing for one round , but only promises invitational strength. Basically this is just a checkback for 3 Spades.

Opener then bids