What defines a Non-Volley Zone (NVZ / Kitchen) fault under official rules?

According to USA Pickleball Rule 9.B, the Non-Volley Zone extends 7 feet from the net on both sides and encompasses the entire 20-foot width of the court. The line itself is considered part of the kitchen; therefore, touching any portion of the 2-inch kitchen line during or immediately following a volley constitutes an immediate fault. Crucially, Rule 9.C dictates that a player's momentum does not terminate until they regain complete, stable physical balance outside the zone. If a player strikes an airborne ball outside the kitchen but their momentum causes a toe, sunglasses, hat, or paddle to contact the line or surface inside the zone, a fault is assessed. Groundstrokes (balls that have bounced once inside the kitchen) may be legally played from within the zone at any time, provided the player does not volley.