PlugThe end with prongs, which goes into an outlet.
ConnectorThe end with slots, which another plug goes into.
BladesThe two flat metal prongs that carry the current.
Ground pinThe third, rounded prong, joined to the ground wire.
Cord jacketThe tough outer covering of the cord.
SlotsOpenings in the face that take the prongs of a plug.
Strain reliefIt keeps a pull on the cord from loosening the wires.
Inside the plug 4
Hot and neutral wiresThe two wires that carry the current, joined to the blades.
Ground wireThe wire joined to the ground pin of the plug.
InsulationThe covering on each single wire inside the cord.
ConductorThe fine metal strands that carry the current.
How this list was compiled: Every name checked on 2026-10-01, a name kept only where two independent sources use it. (1) Wikipedia, text only, counted once: https://en.wikipedia.org/wiki/Extension_cord (a plug at one end and at the other one socket or more; jackets; insulation; the wires inside), https://en.wikipedia.org/wiki/NEMA_connector (blades, informally prongs; the ground pin; the small hole near the tip of the power blades; receptacle slots; hot, neutral and grounding conductors), https://en.wikipedia.org/wiki/Power_cord (a molded plug at one end and a female connector at the other; strain relief; exterior jackets) and https://en.wikipedia.org/wiki/AC_power_plugs_and_sockets (one contact carries the current from the source and another carries it back; a third contact for ground). (2) UL 817, Standard for Cord Sets and Power-Supply Cords (2014 edition, read in the public copy on the Internet Archive), https://archive.org/details/pub.cfr.ul.s817.11.2014 : attachment plug (a male contact device), cord connector (a female contact device wired on flexible cord), blades, the grounding blade or pin, the body of the plug, strain relief, the outer jacket of the cord, the slots in the face of a cord connector, current-carrying conductors and the grounding conductor, insulation. (3) United States Occupational Safety and Health Administration, public domain: Controlling Electrical Hazards (OSHA 3075), https://www.osha.gov/sites/default/files/publications/osha3075.pdf (insulation on conductors; hot wires; the neutral or grounded conductor; the grounding conductor; a three-prong plug), and the Flexible Cords page of the construction eTool, https://www.osha.gov/etools/construction/electrical-incidents/flexible-cords (strain relief; cord connectors; flexible cords are finely stranded; extension cords of the 3-wire type). Read for the names only: no rule or instruction from any of them is repeated on the page. Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work
How it works
The parts of an extension cord are a plug at one end, a connector at the other and a jacketed cord between them. Label the parts of an extension cord with three wires, outside and then inside.
Read the full guide
The whole cord
The plug has two flat blades and a rounded ground pin. A ribbed strain relief sits where the cord leaves it. The cord jacket covers the whole length. At the far end the connector has slots that take the prongs of another plug.
Inside the plug
Three wires leave the cut end of the jacket. The hot and neutral wires run to the two blades, and the ground wire runs to the ground pin. Each wire is a conductor of fine metal strands inside its own insulation.
Jacket or insulation? Insulation covers one wire; the jacket covers all three.
Blades are often called prongs, as in a three-prong plug.
Questions and answers
What are the two ends of an extension cord called?
The end with prongs is the plug, the male end. The end with slots is the connector, or cord connector, the female end, which another plug goes into.
What is the third prong on an extension cord?
The rounded third prong is the ground pin. Inside the plug it is joined to the ground wire, which runs the length of the cord to the matching opening in the connector.
How many wires are inside an extension cord?
A grounded cord has three: a hot wire, a neutral wire and a ground wire. A cord with a two-prong plug has only the hot and neutral wires.
What is the strain relief on a cord?
The collar where the cord enters the plug or the connector. It takes the pull when the cord is tugged, so the strain does not reach the fine strands joined to the screws inside.