Light Bulb Glossary Terms and Definitions

When searching for information on Light Bulbs there are several words you might come across that you’re not familiar with. To help ease the learning curve we’ve assembled this Light Bulb Glossary which covers the most common lightbulbs terms and definitions.

Ampere (amp): A standard unit for the measurement of current.

ANSI: American National Standards Institute

Average Rated Life: A rating in hours of the expected amount of time until the lamp fails.

Ballast:An electrical component used with fluorescent lights to supply proper voltage to the lamp and to regulate the current.

Ballast Factor (BF): The light output of a ballast. BF of 0.90 yields 90% of a lamp’s rated lumens.

Ballast Losses: Power consumed by a ballast that is wasted, as it is given off as heat.

Base: Lamp base that conducts electricity to the lightbulb, lamp.

Beam Angle: Beam spread – the angular spread of the cone of light

Bipin: An IEC standard for lamp fittings. Two pins are on the end of the lamp, for two filaments to start fluorescent lamps and some small incandescents.

Bulb: A glass or quartz glass enclosure which contains a vacuum or gas and a means of light generation (filament ir electrode).

Candela (cd): Unit of light intensity in a specific direction.

Center Beam Candlepower: Candela. A measure of luminous intensity

Compact Fluorescent Lamp (CFL): A small fluorescent lamp made with a glass tube. High color illumination, saves energy. Some are made with an integral ballast.

Color Rendering Index (CRI): The higher the number, the truer the color. Similar to White Balance on digital cameras. CRI of 90 is available.

Color Temperature (CT): Measured in Kelvin. The higher the temperature, the cooler the color. “Warm” light sources have a low color temperature of 2000-3000K, more light in the red/orange yellow range. “Cool” light sources have a color temperature of over 4000K, which is more in the blue light range.

Current: The flow of electricity measured in amperes.

Efficacy: A measure of light output to energy consumption.

Electronic Ballast: A ballast that uses solid state circuitry to raise the frequency to 20,000 hertz or higher, which eliminates “flicker”. This also has a beneficial effect on the gas in the lamp and overall increases efficiency.

Energy: The ability to do mechanical work, measured in kilowatt-hours.

Energy Star: A joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy helping to save money and to protect the environment through energy efficient products and practices. A voluntary labeling program designed to identify and promote energy-efficient products to reduce greenhouse gas emissions.

Filament: A material, usually tungsten, that lights when electric current flows through it.

Floodlight: A lamp which throws off a wide beam, thus “flooding” an area with light.

Fluorescent Lamp: A lamp that lights by electricity flowing through a gas.

Footcandle: The amount of light reaching an object.

Glare: A condition of light coming directly into the eye.

Grounding: A connection between the electrical circuit and the earth, a reference point in electronic circuits.

Halogen Lamps: A lamp made of sealed quartz containing an inert gas and a tungsten filament. It is brighter, more efficient, and burns hotter than a regular incandescent.

High bay: A type of lighting where the ceiling is 20 feet or higher.

High Intensity Discharge (HID) Lamps: A lamp wherein an arc passes between two cathodes in a pressurized tube, causing metal additives to vaporize and throw off a high amount of light.

Illuminance:The light incidence on a surface.

Incandescent Lamp: A lamp that generates light using a tungsten filament heated to white heat by passing current through it. It produces much more heat than light and is very inefficient.

Lamp: lightbulb, tube, etc – the actual part that gives visible light. Also, a term for the complete unit including fixture and bulb, tube, etc.

Lamp Flicker: A stroboscopic effect where a lamp’s light is not a consistent, steady output.

LED: Light emitting diode. LED lamps are mostly made up of several LEDs. They are costly but highly efficient.

Lumens: A unit of overall light output. A candle provides about 12 lumens, a 60 watt lightbulb 840 lumens.

Luminaire: The complete light fixture – housing, lamp, reflector, ballast, socket, lens.

Luminance: A measure of surface brightness measured in candelas per square meter, or per square foot.

Lux (lx): a unit of illumination equal to the direct illumination on a surface that is everywhere one meter from a uniform point source of one candle intensity or equal to one lumen per square meter.

PAR Lamps: PAR is an acronym for parabolic aluminized reflector. They may be incandesent, halogen, or HID and rely on both the internal reflector and prisims in the lens to control the light beam.

Power: Volts x Amps = Watts, or VA. The rate at which energy is consumed.

Quartz: Fused silica, which is melted sand. Although it looks like glass and is similar, it can contain high temperature and pressure. It is used in many types of lamps, such as halogen and HID.

Reflectance: The ratio of light reflected from a surface to that placed upon it.

Reflector: The part of a fixture that reflects the light of the lamp.

Reflector lamp: A lamp with a built in reflector source, such as in PARs.

Spectrum: The range of all possible electromagnetic radiation frequencies.

Voltage: A measure of electromotive force, potential power, analogous to pressure in a water source.

Watt: A unit of electrical power. In lamps, the rate at which they consume energy. In choosing any lamp, this is important.

*Light Bulbs Glossary last updated November 2009. As new terms are discovered their definitions will be added to this page.