Lighting Glossary

Commercial lighting glossary

Commercial lighting uses a handful of terms over and over. This glossary explains them in plain language so a product page, a bid, or a lighting layout is easier to read. It is a companion to our lighting resources and to a lighting layout request. If a term on a product page still is not clear, contact us.

Lumens

Lumens describe how much light a fixture produces, not how much power it uses. Watts tell you about power. Two fixtures with the same wattage can deliver different lumens, and a higher lumen number is not automatically better if the light is aimed poorly or is uncomfortable in the space. For a lot, start with our parking lot lighting guide. For a shop, see the shop lighting guide.

Foot-candles and uniformity

A foot-candle is a common way to describe how much light reaches a surface, such as a floor, a desk, or a parking stall. Uniformity describes how even that light is from one spot to another. A plan can look bright in the middle and still leave aisles or corners too dim. Required or recommended levels come from your project documents, the designer’s goals, or local rules — not from a generic chart on this page. If you have a target, include it in your layout request.

Color temperature and CRI

Color temperature, measured in kelvin (K), describes whether the light looks warmer or cooler. Many commercial sites use a neutral or cooler white. The more important step is to keep one color temperature throughout the space so the site looks consistent. Our color temperature guide walks through the common choices for offices, shops, and outdoor areas, including office lighting and auto shop lights. CRI, or color rendering index, describes how accurately a light source shows colors compared with a reference. When CRI matters for a job — such as finishes in a shop — check the product page rather than assuming every fixture is the same.

Beam, distribution, and cutoff

Beam angle and light distribution describe where the light goes, not just how bright the fixture is. A wide distribution can cover an open floor. A tighter or shaped pattern may be a better fit for an aisle, a roadway, or a lot that has to limit spill light. Full cut-off styles, common on some LED wall packs and area lights, aim light downward to reduce glare and sky glow. Confirm the pattern and mount on the product page, and see mounting options if you are matching a fixture to a pole or a wall.

CCT, wattage, and selectable fixtures

Some fixtures let you select wattage, color temperature, or both after the fixture is installed. That can be helpful when you want to adjust output once you see the space. Selectable does not mean unlimited. The available settings are listed on the product page, and those are the settings you should plan around.

Voltage, drivers, and dimming

The driver is the part of an LED fixture that converts incoming power to what the LEDs need. The voltage range is listed on the product page. Many commercial fixtures are made for a common 120–277V range, but that is not universal, and a 120–277V fixture is not a 480V fixture. Read 277V and 480V LED lighting and shop 480V lighting only when the product is listed for the supply you have. If a fixture is dimmable, the product page will say so and will usually name the dimming type. Do not assume a wall dimmer at the site will match.

Ratings, listings, and controls

Dry, damp, and wet location ratings, along with IP codes, describe how a fixture is meant to handle moisture and dust. Those ideas are covered in IP ratings and wet locations. Safety and efficiency listings, when a fixture has them, appear on the product page and are discussed on our certifications and listings page and in the DLC listing and utility rebate guide. A photocell turns a light on at dusk and off at dawn. A motion or occupancy sensor reacts to activity. Both are explained in photocells and motion sensors.

If you are replacing older HID fixtures, the metal halide to LED replacement chart is a practical starting point, but the final choice should still match the space and the product page. More buying questions are answered in our FAQs. Every fixture is backed by our 5-year warranty and 60-day returns, and orders ship in 1–3 business days per the shipping policy.