Conductor

A material in which an electric current can pass easily. In general, metals are good conductors. Materials that prevent electric currents from passing are called insulators. Therefore insulators have the opposite properties of conductors: They do not allow electric currents to pass through them easily.
Copper and aluminum are the metals most commonly used as electrical conductors. They are manufactured in different forms, the most familiar being drawn wire often coated with thermoplastic or other insulating material to prevent accidental contact with other materials and people. This insulated conductor is often grouped with others in a cable assembly and covered with an outer sheathing such as Type NM Cable (nonmetallic sheathed cable) known in the electrical trade as Romex cable.
Copper and aluminum conductors are also manufactured in bus bar form commonly found in electrical equipment such as load centers, panel boards, meter centers, and switchgear.

A conductor having no covering or electrical insulation whatsoever.

A conductor encased within material of composition or thickness that is not recognized by this Code (National Electrical Code) as electrical insulation.

A conductor encased within material of composition and thickness that is recognized by this Code (National Electrical Code) as electrical insulation.

A pipe inside the building that conveys storm water from the roof to a storm or combined building drain.