What's the LED general techical terms?

• Brightness
  Often used incorrectly with respect to illumination as a synonym for luminous flux, an objective measurement of the visible power of a light source. The term is correctly used when describing screen brightness in a display or television

• Color Rendering
  A general expression for the effect of a light source on the color appearance of objects.

• Color Rendering Index (CRI)
  A measure of the degree of color shift objects undergo when illuminated by the light source as compared with those same objects when illuminated by a reference source of comparable color temperature. The reference source has a CRI of 100.

• Color Spectrum / Visible Spectrum
  The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye, typically between 390nm and 750nm.

• Color temperature
  The description used to describe the effect of heating an object until it glows incandescently, the emitted radiation, and apparent color, changes proportional to the temperature; easily envisioned when considering hot metal in a forge that glows red, then orange, and then white as the temperature increases.

• Directional Light Source
  A light source that emits light only in the direction it is pointed or oriented.

• Efficacy
  The light output of a light source divided by the total electrical power input to that source, expressed in lumens per watt (lm/W).

• Flux / Luminous Flux
  Luminous flux is the measure of the perceived power of light, adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.

• Forward voltage
  A widely accepted printed circuit board (PCB) material which is fiberglass reinforced epoxy laminates that are flame retardant.

• Goniophotometer
  A photometric device for testing the luminous intensity distribution, efficiency, and luminous flux of luminaires.

• Lumen (lm)
  The international (SI) unit of luminous flux or quantity of light and equals the amount of light that is spread over a square foot of surface by one candle power when all parts of the surface are exactly one foot from the light source. For example, a dinner candle provides about 12 lumens.

• Lumen Maintenance
  The luminous flux at a give time in the life of the LED. This is expressed as a percentage of the intial luminous flux.

• Lumen Maintenance Curve
  A graph illustrating the predicted average light output behavior over time of a single LED or solution.

• Luminous Efficiency
  The percentage of total lamp lumens that a lighting fixture, luminaire, or system emits, minus any blocked or wasted light.

• Power Factor
  The active power divided by the apparent power (i.e., product of the rms input voltage and rms input current of a driver).

• Ultraviolet (UV)
  Electromagnetic radiation with wavelength shorter than that of visible light.

• Ingress Protection grade(IP grade)
  IP grade is that the lamps was graded according to their dust-proof, anti-moisture characteristics .it was composed with two numbers, the first number represents the dust-proof and foreign objects intrusion degree of the lamp (0-6 grade),the second number represent the anti-moisture and waterpoof degree of the lamp (0-8 grade), the larger the number, the higher level of protection.