One No Trump (4)

Dealer South, NS Vulnerable

South	West	North	East
Bidding
1NT	No	2♦⁽¹⁾	No
2♥⁽²⁾	No	2♠⁽³⁾	No
3♦⁽⁴⁾	No	3♥⁽⁵⁾	No
3NT⁽⁶⁾	No	No	No

Explanations

⁽¹⁾ Here North's good intermediates and slightly stronger hand is worth a strong invitation to game, so North uses the 2-Way 2♦.

⁽²⁾ South assumes it's a Transfer to Hearts and bids accordingly.

⁽³⁾ Now the 2♠ rebid shows the invitational enquiry.

⁽⁴⁾ South is better than minimum and so bids their lowest 4-card suit at the 3-level.

⁽⁵⁾ North shows his 4-card Hearts.

⁽⁶⁾ With no Heart fit and no 4-card Spades South signs off in 3NT.