Any raise of opener's suit is to play and could be preemptive. A 3NT response is also to play. A new suit response is forcing one round and shows at least a five-card suit. Opener should raise a major suit response with a three-card fit, or perhaps with a doubleton honor. With a maximum weak two-bid, name a new suit or bid notrump.
Responses show the number of aces by steps.
A jump overcall of 2NT shows at least 5-5 in the lower two unbid suits. A cuebid overcall when the opponents have bid two suits is natural in either suit. Responder can bid 2NT over a major suit cuebid to ask for partner's minor. Reopening bids mean much the same as direct seat bids, though they can be lighter at the minimum end. A reopening 1NT after an opponent has opened shows 10-15 points.