LED lamps and LED light fixtures have special terminologies and definitions. Below are some lighting terms related to LED technology and lighting in general. It is important to know and understand these terms when choosing an LED light bulb or fixture to make sure the correct product is chosen.

Light Source

The light source is the technology that emits light for the bulb or fixture. Different lighting technologies include LED, incandescent, fluorescent, metal halide, high pressure sodium, halogen and mercury vapor. Out of all these, LED technology is the most energy efficient and has the longest rate life.


A footcandle is the illuminance on a one square foot surface from a uniform source of light. Footcandles are the unit of measurement used by lighting professionals to calculate the light levels for commercial and outdoor spaces. Certain footcandle levels are recommended for different types of areas and tasks to ensure the appropriate light levels are met.


The lumens is the term used for the brightness or the amount of light an LED bulb or fixture produces. How bright an LED fixture is will be determined by how much the lumens is.


The level of electric power or consumption is measured by the wattage. The wattage is measured in watts and is calculated by multiplying voltage to the ampere.

Color Temperature

The color temperature is a way of describing the light color by using kelvins, the unit of measure for temperature. Color temperatures are characterized as: warm white, which can range anywhere from 1700K to 3000K; cool white, which can range anywhere from 3500K to 5000K; and daylight, which is 5700K and above. A lower the kelvin value emits a warmer or more yellow the light, while a higher value will result in a cooler and more bluish light.

Input Voltage

The input voltage is the required electric power required for the fixture to work. A light fixture can use either line voltage or low voltage to work. Line voltage is the standard 120-277V from regular outlets, while low voltage is normally achieved through a transformer to get 12-24V.


The color rendering index or CRI is the way to measure how accurately a light source can display the true color of an object when compared to natural lighting. Higher numbers mean that this light source is close to natural light. Numbers that are higher than 80+ CRI are very well in being the most similar to natural light.


Efficacy is measured in lumens per watt (lm/W) and closely resembles how energy efficient a lighting fixture is. A higher efficacy means the fixture produces more lumens with lower wattage.

Dimming Control

Dimmable LED fixtures are compatible with specific dimming technologies that work differently. Triac dimming uses the regular LED/CFL or incandescent dimmers, while 0-10V dimming requires a 0-10V current to control the light intensity level. Other types of dimming include reverse phase dimming, forward phase dimming and low voltage dimming.

Housing Construction

LED fixtures are made of sturdy material built for indoor or outdoor use like die-cast aluminum, stainless steel, polycarbonate, thermoplastic.

Lens Type

The lens of the fixture that covers the LED can be made of glass, acrylic or polycarbonate, and can have a clear or frosted diffuser to disperse the light.

Operating Temperature

The temperature at which the LED bulb or fixture will operate effectively.

Rate Life

The rate life of an LED fixture is measured as the time it takes until the lumen maintenance or light output reaches 70% of the initial output (L70). The LED lifespan is measured in hours and the standard for all LED fixtures is an L70 of 50,000 hours.

Lighting Glossary

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