* A light bulb: This seems obvious, but it's the source of light! Make sure it's the correct type for your fixture.

* A light fixture: This holds the bulb and provides a way to connect it to the electrical system.

* Electrical wiring: This carries the electricity from the power source to the light bulb.

* A power source: This provides the electricity to light the bulb, typically a wall outlet.

* A switch: This allows you to control the flow of electricity to the bulb, turning it on and off.

So, you need a complete circuit: power source, wiring, switch, fixture, and bulb.