Partner opens 1NT and you have 5 or more cards in a minor suit. What should you do?
Unfortunately, some of this depends on methods. You need to know how your partnership shows a minor. Do you play 4-suit transfers? There are many possibilities, but for this article, let's assume you use what is currently most popular:
1NT-2 = Range ask or Clubs
1NT-2NT = Transfer to Diamonds
After 1NT-2, opener bids 2NT with a minimum or 3 with a maximum. If the responder just has an invite to 3NT (like a flat 9-count), he either passes 2NT, or converts 3 to 3NT. If responder has clubs, he can pass 3 to make that the contract, or bid anything but 3NT (showing clubs).
You and your partner should also discuss what it means in each of these situations:
1) You start with 2 or 2NT and next bid a major suit on the 3-level. For example:
One possibility is "natural" (5+ and 4).
Another possibility is "shortness" with a hand such as:
2) What does it mean it you start with Stayman and later bid a minor?
Is that forcing, invitational or sign-off?
This area can get complicated (as hinted at above), but none of it is the purpose of this article.
All I want to show here is if/when you should actually show your minor.
So, partner opens 1NT and you hold each of the following hands:
With #1, Pass and let partner suffer. You "never" transfer to a minor with a flat (5-3-3-2) hand. The only possibly exception might be if you wanted to eventually look for a slam.
With #2, you want to play in 3. That has to be better than 1NT. It is now just a matter of methods. Make sure you and your partner know how in your system the responder signs off in 3-of-a-minor
With #3, you want to look for a 4-4 spade fit and if it isn't found, show your clubs. Again, you have to know how to do this in your system. Do you start with Stayman and then bid 3? Do you start with a transfer to clubs and then bid your spades?
With #4, you have no interest in playing in your minor. Just bid 3NT. You can "show" your diamonds when you table the dummy.
With #5, again you have no reason to show the minor in the auction. Just raise 1NT to 3NT (or, if you play Puppet Stayman, you can look for a 5-3 spade fit).
This article just covers some basics. In the real world, there is much more confusion awaiting you. For example, what do you do with a very weak hand with a 4-card major and a 6-card minor? Hint: It depends on your system/agreements.
Here is a summary of your approach when you hold a 5+ card minor and partner opens 1NT:
No game interest
With only a 5-card minor, usually pass 1NT.
With a 6+ card minor, transfer to play in 3 of the minor
With a 5-card minor and no 4-card major, just invite in notrump
With a 5+card minor and a 4-card major, start with Stayman
With a 6-card minor (and no 4-card major), start with a transfer (likely your methods will allow opener to show min/max)
With a flat hand, don't bother showing the minor unless you have slam interest
With shape (6+ card minor or 4-card major and 5+ card minor), use Stayman or a transfer to start