Bridge & other card games/Bridge
Please consider this questiom:
Opener bids 3 hearts, having 7 of them and 6 points. Opponent passes. Partner bids 3 spades. Is opener to consider partner's bid as having 13 points and 4 spades?
Opener should consider partner to have at least 16 points and at least 6 good spades.
A primary purpose of the bridge auction is to determine what is the best trump suit for your side. When partner opens 3H showing a decent 7 card heart suit and about 6-10 points, that heart suit becomes the prime candidate for your best trump suit. It is likely that your side has more cards in hearts than in any of the other suits and partner's hand may have very little value if trumps are any suit other than hearts. In order for you to suggest a different suit (for example spades) your suit should be at least approximately as good as opener's hearts. Therefore, to bid 3S your spades should be at least 6 cards long with 2 of the top 3 honors. Also, since you are basically forcing the auction to the four level, your hand should be strong enough to give your side a reasonable prospect of taking 10 tricks. Given that your partner is weak, your hand should have 16 points or more.
Bridge bids should have a constructive purpose. After opener opens 3H showing seven hearts, the likelihood that his hand also contains 4 or more spades is minimal. Therefore there is no constructive purpose in responder bidding 3S with only a 4 card suit since it is extremely unlikely that spades will turn out to be a better trump suit than hearts.