noun
lumen
LOO-muhn
noun
1
The standard unit for measuring the total amount of visible light emitted by a source.
"The torch is rated at 800 lumens."
2
The hollow space inside a tube or tubular body part, such as a blood vessel or needle.
"Plaque had narrowed the lumen of the artery."
How to Use Lumen
Learner’s notesIn plain EnglishA measure of brightness, or (in anatomy) the open channel running through a tube-shaped structure.
Common pairings
800 lumens
lumen output
narrowed lumen
Word Forms
lumens plural, lumina plural
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The torch is rated at 800 _____.
Etymology
Borrowed from Latin lumen, "light" or "opening." It was first adopted as a scientific unit of light by the French physicist André Blondel in 1894.