Here’s a few basic NEC(National Electrical Code) definitions(Article 100)
Ampacity. The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.
Energized. Electrically connected to, or is, a source of voltage.
Exposed (as applied to live parts). Capable of being inadvertently touched or approached nearer than a safe distance by a person. It is applied to parts that are not suitably guarded, isolated or insulated.
Grounded (Grounding). Connected (connecting) to ground or to a conductive body that extends the ground connection.
Luminaire. A complete lighting unit consisting of a light source such as a lamp or lamps, together with the parts designed to position the light source and connect it to the power supply. It may also include parts to protect the light source or the ballast or to distribute the light. A lampholder itself is not a luminaire.
Neutral Conductor. The conductor connected to the neutral point of a system that is intended to carry current under normal conditions.
Ungrounded. Not connected to ground or to a conductive body that extends the ground connection.
Voltage (of a circuit). The greatest root-mean-square (rms) (effective) difference of potential between any two conductors of the circuit concerned.
Voltage to Ground. For grounded circuits, the voltage between the given conductor and that point or conductor of the circuit that is grounded; for ungrounded circuits, the greatest voltage between the given conductor and any other conductor of the circuit.