Glossary of Terms

Terminology Description
Beam Angle It is the angular dimension of the cone of light from reflectorized lamps encompassing the central part of the beam out to the angle where the intensity is 50% of maximum.
Bulb A bulb is normally referred to a lamp. It refers to the outer glass bulb containing the light source.
Candela The measure of luminous intensity of a source in a given direction. A light source has different intensities depending upon the direction considered.
Correlated Colour Temperature (CCT) A specification of the colour appearance of a lamp relating its colour to that of a reference source heated to a particular temperature, measured in degrees Kelvin (K).
Chip A very small square of semic conduction material. Also known as a “die”, it is the “active” light-emitting component of an LED.
Colour Rendering Indicator It is the measure of a light source's ability to render the "true" colour of objects as compared with a reference source with comparable colour temperature.
Colour Temperature The colour temperature of a light source is defined in comparison with a "black body radiator" and plotted on a "Planckian curve". Yellowish-white or warm sources, like incandescent lamps, have lower colour temperatures (2700K-3000K); white and bluish-white or cool sources, such as cool white (4500K) and natural daylight (6000K), have higher colour temperatures.
Cool white It means a colour temperature of around 4500K or higher.
Colour rendering Index (CRI) The colour rendering index is a measure of the correspondence between the colour of an object and its appearance under a light source.
Drivers Circuits that transform line voltage into a constant current for operating the LEDs.
Heat Sink A heat sink is an enclosure that serves to radiate the heat from the LED lamp. Materials with good thermal conductivity are used here to transfer the heat generated inside the lamp to the surrounding air.
Illuminance The density of light arriving on a surface. Illuminance is measured in footcandles or lux.
Incandescent Lamp A light source that generates light utilizing a thin filament wire heated to white heat by an electric current passing through it.
Kelvin A unit of temperature starting from absolute zero, parallel to the Celsius scale.
Kilowatt [kw] The measure of electrical power equal to 1000 watts.
Kilowatt Hour [kWh] The standard measure of electrical energy and the typical billing unit used by electrical utilities for electricity use. A 100-watt lamp operated for 10 hours consumes 1000 watt-hours (100 x 10) or one kilowatt-hour. If the utility charges 0.17 €/kWh, then the electricity cost for the 10 hours of operation would be 17 cents. (1 x 0.17 €)
Lamp The term used to refer to the complete light source package, including the inner parts as well as the outer bulb or tube. It is also commonly used to refer to a type of small light fixture such as a table lamp.
LED Light Emitting Diodes or LED is a semiconductor device that illuminates by the movement of electrons in the material. It is a solid that directly converts electrical impulses into light. Most white light LEDs incorporate phosphors to change the colour characteristics of the emitted light.
Luminaire It is a complete lighting unit consisting of a lamp (or lamps), ballast (or ballasts) as required together with the parts designed to distribute the light, position and protect the lamps and connect them to the power supply. A luminaire is also called a fixture.
Luminous flux (lm) Luminous flux or luminous power is the measure of the perceived power of light. It is non-directional.
Luminous Intensity Luminous intensity indicates the strength of light in a particular direction and is presented in candela (cd).
Lux (lx) A unit of illuminance or light falling onto a surface. One lux is equal to one lumen per square meter. Ten lux approximately equals one footcandle.
Organic light emitting diode An organic light emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compounds which emit light in response to an electric current.
Phosphor An inorganic chemical compund processed into a powder and deposited on the inner glass surface of fluorescent tubes and some mercury and metal-halide lamp bulbs. Phosphors are designed to absorb short wavelength ultraviolet radiation and to transform and emit as visible light. Phosphors are also used in LED devices to create white light when used in combination with LEDs of certain wavelengths.
Warm white A yellowish-white light having a colour temperature of around 2700 - 3500K.
Watt A unit of electrical power. Lamps are rated in watts to indicate the rate at which they consume energy.