massless

[ mas-lis ]
/ ˈmæs lɪs /
|

adjective Physics.

pertaining to an elementary particle having zero rest mass, as a photon.

Origin of massless

First recorded in 1875–80; mass + -less
Related formsmass·less·ness, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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