The Article 100 of NEC covers essential definitions used throughout the code to ensure clear understanding and consistent application. The terms outlined in the article appear throughout the Code. Here are the key definitions from NEC Article 100, explained for clarity.

Key Definitions from Part I (General):

1. Accessible (as applied to equipment): Equipment that can be reached for operation, renewal, or inspections without removing building materials or structures.
2. Accessible (as applied to wiring methods): It can be removed or exposed without damaging the building structure or finish or not permanently closed in by the structure or finish of the building. Refers to whether anything in the building has to be altered to get to the wiring.
3. Accessible, Readily (readily accessible): Equipment that can be quickly reached without obstacles or ladders. This term mostly refers to how quickly equipment can be accessed.
4. Ampacity: The maximum current, in amperes, that a conductor can carry continuously without exceeding its temperature rating.
5. Appliance: Utilization of non-industrial equipment built in standardized sizes or types that performs functions such as cooking or air conditioning.
6. Authority Having Jurisdiction (AHJ): The organization or individual responsible for enforcing codes or approving materials and installations.
7. Bonded (Bonding): Connecting metallic parts to establish electrical continuity and conductivity.
8. Branch Circuit: The conductors between the final overcurrent device and the outlet(s).
9. Circuit Breaker: A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically when overcurrent occurs, without damage to itself.
10. Conductor (Bare, Covered, Insulated): A material that allows the flow of electrical current, categorized as bare (no covering), covered (encased in a non-insulating material), or insulated.
11. Continuous Load: A load where the maximum current is expected to continue for 3 hours or more.
12. Ground (Grounding): A conducting connection to the earth or to some conductive body that serves as a substitute for the earth.
13. Grounding Conductor: A conductor that connects electrical equipment or the grounded part of a wiring system to a grounding electrode, which is typically a metal rod or plate buried in the ground, to ensure the safe dissipation of electrical currents.
14. Ground-Fault Circuit Interrupter (GFCI): A device intended to protect personnel by de-energizing a circuit when current to ground exceeds a specific threshold (typically 6 mA).
15. Overcurrent: Current exceeding the rated current of equipment or conductor ampacity, including overloads and short circuits.
16. Feeder: All conductors between the service equipment and the final branch-circuit overcurrent device.
17. Disconnecting Means: A device or group of devices by which a circuit can be disconnected from its power source.
18. Location, Damp: Locations protected from the weather but subject to moderate moisture, such as under canopies or in some basements.
19. Location, Dry: Locations are not normally subject to dampness or wetness but are temporarily exposed to moisture, such as during building construction.
20. Location, Wet: Locations subject to saturation with water or other liquids, such as vehicle washing areas or outdoor installations.
21. Solar Photovoltaic System: A system of components and subsystems that convert solar energy into electrical energy suitable for use in a building or for connection to a load.

Key Definitions from Part II (Over 600 Volts, Nominal):

1. Fuse: An overcurrent protection device with a circuit-opening fusible part that is heated and severed by overcurrent.