If you answered "grounding," you got the
wrong answer. Article 250 provides the requirements for grounding
and bonding. That's an important distinction, because many
people misapply grounding in place of bonding. This creates
enormously expensive problems as well as dangers to people.
[250.2] It's an intentionally constructed,
permanent, low-impedance path for current under ground fault
[250.2] A ground fault is an unintentional
connection between an ungrounded conductor and bonded metallic
objects (which the NEC refers to as "grounded," but see the Article
100 definitions of "grounded" and "bonded").
[250.2] It's the path electricity takes in the
event of a ground fault. What you want is an intentional
ground fault path that directs ground fault current properly.
Otherwise, the ground fault path may include people and equipment.
[250.2 FPN] Examples include piping, metal
frameworks, cable sheaths, ductwork, and other conducting bodies.