After a Weak-Two by the opponents followed by a Takeout Double and a pass by responder, 2NT is a conventional response, requesting (but not insisting) on a relay to 3♣. This allows Advancer to distinguish between minimum, intermediate, and maximum hands.
(2♠)X(p):
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2NT: Relay to 3♣
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pass, 3♦, 3♥: to play (7 or fewer HCP)
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3♠: 4 hearts, spade stopper, GF
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3NT: to play, no heart suit, stopper
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The 3♣ Relay may be bypassed with 22+ HCP or 9+ playing tricks
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3♣, 3♦, 3♥: semi-positive (8-11 HCP)
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3♠: game values, 4 hearts, no stopper
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3NT: game values, no heart suit, no stopper