R A I S E   W I T H   T H R E E
Three With an Honor is Good!

You open a minor and your partner responds with a major
If you are of the old school you will rebid 1NT with this hand...   This is neither a convention nor a treatment, but it is a popular agreement and it has a problem.

After everyone passes you often see a dummy similar to one of these.  Too bad.

Bridge has lots of rules and guidelines which for the most part will help you make the best decision, but the rule that you need 4-card support to raise your partner's response has been revisited.  Of course, there are new guidelines if you are going to raise with three because sometimes you should rebid 1NT.
    You should have an honor and generally a small doubleton somewhere else in the hand.
This agreement can be as simple as the above, but of course bridge players like to get fancy...  There is a way for responder to determine if his partner raised with three:
    3344 -- We have the Thirtythree Fortyfourconvention!

Opener     Partner     Meaning
    1    1
    2    2NT Tell me more, partner
    3 I have 3-card support and a minimum hand
    3 I have 3-card support and a good hand
    3 I have 4-card support and a minimum hand
    3 I have 4-card support and a good hand

How your partnership defines a good hand is up to you, but you might consider 15+ points as a good hand.

If you would like to see more discussion on this subject, try:  

Roy Wilson