blue light
Americannoun
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a band of the visible light spectrum that has a shorter wavelength and produces higher energy than other colors of light: occurring in sunlight and emitted by electronic devices that use LED technology.
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American History, Usually Disparaging. Also Blue Light a member of a faction of the American Federalist party considered disloyal for opposing the War of 1812: so called from the claim that they flashed blue light signals to alert the British to the presence of blockade runners.
Etymology
Origin of blue light
First recorded in 1810–15
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
In 2020, Longcore co-published a study linking artificial night light, including blue light emitted by LEDs, to cancer.
From Los Angeles Times • May 8, 2026
Depending on the situation, a Tesla will gently warn with a message and a flashing blue light on the center screen, buzz, or require pressure on the steering wheel.
From Barron's • May 3, 2026
The researchers generated 19 new variants that showed greater sensitivity to light, reduced activity in darkness, or the ability to respond to green light rather than only blue light.
From Science Daily • Mar. 9, 2026
“Melatonin is what makes you sleepy. The effect of the blue light is that it makes you more awake and alert.”
From The Wall Street Journal • Nov. 25, 2025
He was walking along a mountain road in the cool blue light of dawn.
From "Harry Potter and the Deathly Hallows" by J.K. Rowling
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
