Jacoby 2NT/H2>

After opponents' opening of one of a major, responder bids 2NT to show four card support and 12+HCP. Opener must rebid, as follows

3 of a new suit show a singleton or void in the suit
3 of agreed major shows 16+ HCP
3NT shows 14-15 HCP
4 of the agreed suit show minimum opening.
4 of new suit shows 5 cards in that suit