lumen

noun

lu·​men ˈlü-mən 

plural lumens also lumina ˈlü-mə-nə 

1

: the cavity of a tubular organ or part

the lumen of a blood vessel

2

: the bore of a tube (as of a hollow needle or catheter)

3

: a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candle intensity

luminal adjective

or less commonly lumenal

ˈlü-mə-nᵊl 

Did you know?

There are two common units for measuring light, the candela and the lumen. Both are recognized as standard international units, which also include the second (for time), the kilogram (for weight), and the meter (for length). The candela is a measure of intensity; an ordinary candle gives off light with the intensity of about one candela. The lumen is a measure of "luminous flux;" a standard 100-watt lightbulb gives off 1500–1700 lumens. Luminous flux indicates how much light is actually perceived by the human eye. Technologies vary in how efficiently they turn electricity into light; halogen lights produce about 12 lumens per watt, ordinary incandescent lightbulbs produce about 15 lumens per watt, and compact fluorescent bulbs produce about 50 lumens per watt.

Examples of lumen in a Sentence

Recent Examples on the Web

The color-changing smart bulbs work with all major smart home platforms and light up homes with 1,100 lumens of brightness. —Sheena Vasani, The Verge, 2 Apr. 2024

At 14,000 lumens per panel, at 100% the Skylight will starkly light every corner of your space. —Anthony Karcz, Forbes, 29 Mar. 2024

Frequently Asked Questions How many lumens are recommended for outdoor use? —Camryn Rabideau, Peoplemag, 19 Jan. 2024

Fluorescent light bulbs are next The Department of Energy proposed a rule in December 2022 that would require minimum lighting efficiency for fluorescent lights from 120 lumens per watt -- more than double the current requirements. —Julia Jacobo, ABC News, 1 Aug. 2023

According to Atwell, most options feature multiple lumens settings, with the higher end being somewhere between 1,000 to 3,000 lumens, as seen with options like the Stanley Fatmax SL10LEDS Rechargeable Spotlight or the Nitecore EDC27 Ultra Slim Flashlight. —Jack Byram, Better Homes & Gardens, 31 Mar. 2024

For reference, a standard 60-watt light bulb gives off about 800 lumens. —Pamela Porter, Better Homes & Gardens, 21 Mar. 2024

Related Our favorite smart home automations How to pick a smart home platform The 60W-equivalent bulbs are plenty bright for most needs at 800 lumens. —Quentyn Kennemer, The Verge, 18 Mar. 2024

The newer camera also has brighter LEDs (that together put out 2,800 lumens vs. 2,600 lumens last generation) which are dimmable and have a 5,000K white color temperature. —PCMAG, 5 Feb. 2024

Word History

Etymology

New Latin lumin-, lumen, from Latin, light, air shaft, opening

First Known Use

1873, in the meaning defined at sense 1

Kids Definition

lumen

noun

lu·​men ˈlü-mən 

plural lumens also lumina -mə-nə 

: a unit of light quantity equal to the light on a unit surface all points of which are at a unit distance from a point source of light having a strength of one candle

Medical Definition

lumen

noun

lu·​men ˈlü-mən 

plural lumina -mə-nə  or lumens

1

: the cavity of a tubular organ or part

the lumen of a blood vessel

2

: the bore of a tube (as of a hollow needle or catheter)

3

: a unit of luminous flux equal to the light emitted in a steradian by a uniform point source of one candle intensity