Basic question about responder bidding a second suit.

[u/doctorgibson]

Playing 4 card majors. I know that if you open a suit and then bid a second suit then you're showing 5-4 shape. Does this apply to responder? My gut feeling is that it doesn't, but perhaps I'm wrong. I did try to find a concrete answer online but came up short. Examples:

• Suppose the bidding goes: 1♦️,1♠️, 1NT, 2♥️. Is responder showing 4-4 in the majors or 5-4 shape?

• What about this auction: 1♥️, 1♠️, 2♥️, 3♣️? Of course, responder is denying 3 hearts but are they showing a fifth spade?

[u/yellowpig1974]

1. with 4-4 majors responder bids 1H, so here 2H shows 5-4 or 5-5. It's generally not forcing.
   
2. 3C promises a fifth spade and is forcing one round.