Knowledge Base

Lighting Terms Simplified

Lumens, Kelvin, CRI, IP ratings and the rest, explained in plain English.

0-10V Dimming: A dimming method common in commercial fixtures, where a separate low-voltage signal controls brightness.

A19: The classic household bulb shape and size.
ADA Compliant: Meets Americans with Disabilities Act guidelines, such as limits on how far a wall fixture projects from the wall.

B10 / B11: Small decorative bulb shapes, often called torpedo or candle bulbs, commonly used with candelabra bases.
Beam Angle: How wide a cone of light a lamp or fixture produces. Narrow beams (around 10–25 degrees) spotlight objects; wide beams (40 degrees and up) wash larger areas.

Candelabra Base (E12): A small screw-in bulb base used in chandeliers, sconces and decorative fixtures.
CCT: Correlated Color Temperature, the technical name for color temperature, measured in Kelvin.
CFM: Cubic Feet per Minute, the amount of air a ceiling fan or exhaust fan moves. Higher CFM means more airflow.
Chandelier: A decorative hanging fixture with multiple lights, often used as a room’s centerpiece.
Color Temperature (Kelvin): Describes how warm or cool white light looks. 2700K is warm and cozy, 3000K is soft white, 3500K is neutral, 4000K is cool white and 5000K looks like daylight.
CRI: Color Rendering Index, a 0–100 score for how accurately a light shows colors compared with natural light. A CRI of 90 or higher is considered excellent.

Damp Rated: Approved for areas with moisture but no direct water, such as bathrooms and covered porches.
Dimmable: A bulb or fixture designed to work with a dimmer. LEDs need a compatible dimmer to dim smoothly without flicker or buzz.
DLC Listed: Listed by the DesignLights Consortium for energy efficiency. Many commercial utility rebate programs require DLC-listed products.
Downrod: The metal pipe that hangs a ceiling fan below the ceiling. Longer downrods are used on higher ceilings.
Driver: The electronic component that powers an LED, converting line voltage to the low-voltage current LEDs need. Similar to a ballast in fluorescent lighting.

Efficacy (lm/W): Lumens per watt, a measure of energy efficiency. The higher the number, the more light you get for the electricity used.
ELV Dimmer: Electronic Low Voltage, or reverse-phase, dimmer. Often recommended for LED fixtures because it dims smoothly at low levels.
ETL Listed: Tested and certified for safety by Intertek’s ETL program, accepted the same way as UL listing.

Fandelier: A ceiling fan combined with a chandelier-style light, usually with enclosed or hidden blades.
Flush Mount: A ceiling fixture that sits tight against the ceiling, good for low ceilings.
Foot-candle (fc): The amount of light landing on a surface, equal to one lumen per square foot. Lighting designers use foot-candles to set light levels for tasks.
Free Jack / Unijack: A canopy and connector system that lets you swap compatible low-voltage pendants without rewiring.

High Bay: A fixture designed for high ceilings, typically 20 feet and up, in warehouses, gyms and industrial spaces.
Hugger Fan: A ceiling fan that mounts flush to the ceiling without a downrod, made for low ceilings.

Integrated LED: A fixture with built-in LEDs instead of a replaceable bulb. Integrated LEDs are designed to last for many years.
IP Rating: Ingress Protection rating. The first digit rates protection from dust and solids, the second from water. IP65, for example, is dust-tight and protected against water jets.

Line Voltage: Standard household voltage, 120V in the United States.
Linear Suspension: A long pendant fixture, often hung over dining tables, kitchen islands and conference tables.
Low Voltage: Lighting that runs on 12V or 24V instead of standard 120V, common in landscape, under-cabinet and some pendant lighting. It usually needs a transformer or driver.
Lumen (lm): A measure of how much visible light a bulb or fixture puts out. More lumens means more light. Compare lumens, not watts, when choosing LED products.
Lumen Maintenance (L70): The number of hours until an LED’s output drops to 70 percent of its original brightness, a common way to rate LED life.
Lux: The metric version of a foot-candle: one lumen per square meter. One foot-candle is about 10.76 lux.

Medium Base (E26): The standard household screw-in bulb base in the United States.
MR16: A small low-voltage reflector lamp often used in track, accent and landscape lighting.

PAR / BR: Reflector bulb shapes. PAR bulbs throw a focused beam; BR bulbs give a softer, wider flood, common in recessed cans.
Pendant: A single fixture that hangs from the ceiling on a cord, chain or rod.
Photocell (Dusk to Dawn): A light sensor that turns a fixture on at dusk and off at dawn automatically.

Sconce: A fixture mounted on a wall.
Semi-Flush Mount: A ceiling fixture that hangs a few inches below the ceiling on a short stem.

Transformer: A device that steps standard 120V household power down to low voltage, used to power low-voltage landscape lighting systems.
TRIAC / Phase Dimming: The most common household dimmer type, also called forward-phase or incandescent dimming. Many dimmable LEDs work with TRIAC dimmers.
Troffer: A recessed rectangular fixture that fits into a drop ceiling grid, common in offices and schools (2×2, 2×4 and 1×4 sizes).
Tunable White: A fixture that lets you adjust its color temperature, for example from warm to cool white.

UL Listed: Tested and certified for safety by UL (Underwriters Laboratories).
Uplighting: Aiming light upward from the ground to highlight trees, columns or architecture.

Wall Grazing: Placing light close to a wall and aiming it along the surface to bring out texture in stone or brick.
Wall Pack: An exterior wall-mounted fixture that lights building perimeters, entrances and parking areas.
Watt (W): The amount of electricity a bulb or fixture uses. LEDs produce the same light as older bulbs while using far fewer watts.
Wet Rated: Approved for locations exposed directly to rain or water, such as uncovered patios and some showers.