lumen

American  

[loo-muhn] / ˈlu mən /

noun

lumens, plural lumina plural

1. Optics. the unit of luminous flux, equal to the luminous flux emitted in a unit solid angle by a point source of one candle intensity. lm

2. Anatomy. the canal, duct, or cavity of a tubular organ.

3. Botany. (of a cell) the cavity that the cell walls enclose.

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lumen British  

/ ˈluːmɪn /

noun

1.  lm.  the derived SI unit of luminous flux; the flux emitted in a solid angle of 1 steradian by a point source having a uniform intensity of 1 candela

2. anatomy a passage, duct, or cavity in a tubular organ

3. a cavity within a plant cell enclosed by the cell walls

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lumen Scientific  

/ lo̅o̅′mən /

lumens plural

1. The central space within a tube-shaped body part or organ, such as a blood vessel or the intestine.

2. The SI derived unit used to measure the amount of light passing through a given area per second. One lumen is equal to the luminous flux passing per unit solid angle from a light source with a strength of one candela.

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Other Word Forms

Derived Forms

• lumenal
  adjective

Inflected Forms

Nouns

• lumens
  plural
• lumina
  plural

Etymology

Origin of lumen

1870–75; < New Latin, special uses of Latin lūmen (stem lūmin- ) light, window

Explanation

The lumen is a unit of measurement for the brightness of light. If a light bulb is blindingly bright, it produces a lot of lumens. The lumen is a basic unit for measuring brightness, just as the gram is a basic unit for measuring mass. A typical light bulb in your home might produce about 1000 lumens. Lumen is related to the word luminous, which means “bright” or “radiant.”

Example Sentences

Levi’s, Gillette, Lumen and others had to go into hiding during the World Cup—and wound up getting more exposure.

From The Wall Street Journal • Jun. 28, 2026

Of the three World Cup venues I've visited, Seattle Stadium - better known as Lumen Field - is the one that ticks the most boxes as the perfect stadium experience for me.

From BBC • Jun. 25, 2026

Iran will close group play against Egypt at Seattle’s Lumen Field on Friday night.

From Los Angeles Times • Jun. 22, 2026

In Seattle, telecommunications company Lumen did its best to turn the situation on its head, filming a tongue-in-cheek video from the stadium it sponsors, normally the home of the NFL's Seahawks and MLS' Sounders.

From Barron's • Jun. 12, 2026

Jefferson Lumen, his wife, and Clare sat on the opposite side of them looking like three angry red-headed dolls gleefully ready to watch her get kicked out.

From "The Marvellers" by Dhonielle Clayton