A glass bulb containing a wire filament (usually tungsten) that emits light when heated; SYN. lightbulb, bulb, incandescent lamp, electric light, electric-light bulb.
Incandescent filament lamp, first demonstrated by Joseph Swan in the UK 1878 and Thomas Edison in the US 1879. The present-day light bulb is a thin glass bulb filled with an inert mixture of nitrogen and argon gas. It contains a filament made of fine tungsten wire. When electricity is passed through the wire, it glows white hot, producing light.