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An alphabetical list of terms in a particular domain of knowledge with the definitions for those terms which are either newly introduced or at least uncommon. Traditionally, a glossary appears at the end of a literary source.


Beam Spread: The angle of light that is emitted through the optical fiber output end.



Candela (CD): A base unit of power emitted by a light source in a particular direction, weighted by the luminosity function. See Lumen.

Candlepower (CP): Used to express levels of light intensity in terms of the light emitted by a candle. See Candela.

CE: The CE marking is a mandatory conformity mark on many products placed on the single market in the European Economic Area (EEA). The CE marking certifies that a product has met EU consumer safety, health or environmental requirements.


Color Rendering Index (CRI): A quantitative measure of the ability of a light source to reproduce the colors of various objects faithfully in comparison with an ideal or natural light source. A color rendering

index number is assigned to a light source based on its ability to make color pigments look as they would under specific test sources when compared to sources that have the same color temperature. Higher numbers indicate better light quality.


Correlated Color Temperature (CCT): The color of light that comes from natural, or white, light expressed in Kelvin (K). The higher the number the bluer the light appears. The lower the number the redder the light appears. Daylight at the horizon is 5000K.

Foot-Candle (FC): The measured extent of light on a given surface.



Illuminance: The amount of light at a certain point on a surface, measured in foot-candles or lux.


LTL: Luminaire TestingLaboratory, Inc. is an independent source of photometric test reports for the lighting industry. Test reports conform to Illuminating Engineering Society of North America (IESNA) standards.


Lumen (LM): A measure of the perceived power of light equal to the light given offuniformly as one candle intensity.

Luminance: A photometric measure of the luminous intensity per unit area of light traveling in a given direction.It describes the amount of light that passes through or is emited from a particular area, and falls within a given solid angle.

Luminous Flux: The measure of the perceived power of light as adjusted to reflectthe varying sensitivity of the human eye to diferent wavelengths of light.

Lux (LX): A unit of illuminance and luminous emitance, which is equal to one lumen per square meter. One footcandle ≈ 10.764 lux


U.L.: Underwriters Laboratories, Inc., is a certifietestinglaboratory that distributes the minimum safety standards for electrical and related products per conformity with the electrical code of the country.








Power Factor

Total Harmonic Distortion (THD)

Rated Life

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