speed of light
noun phraseDefinition of speed of light
: a fundamental physical constant that is the speed at which electromagnetic radiation propagates in a vacuum and that has a value fixed by international convention of 299,792,458 meters per second
—symbol c
Keep scrolling for more
Comments on speed of light
What made you want to look up speed of light? Please tell us where you read or heard it (including the quote, if possible).
Test Your Vocabulary
Musical Words Quiz
- Which word describes a musical performance marked by the absence of instrumental accompaniment?
Can you spell these 10 commonly misspelled words?
TAKE THE QUIZ
Test Your Knowledge - and learn some interesting things along the way.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridgedWords at Play
Ask the Editors
Share speed of light
Time Traveler for speed of light
The first known use of speed of light was in 1823
See more words from the same year