Adjective
massless (not comparable)
Having no mass.
The photon is a massless particle.
The color gauge theory postulates the existence of eight massless particles, sometimes called gluons, that are the carriers of the strong force just as the photon is the carrier of the electromagnetic force. Sheldon L. Glashow
Additionally, it can be shown that any massless spin-2 field would give rise to a force indistinguishable from gravitation, because a massless spin-2 field would couple to the stress–energy tensor in the same way that gravitational interactions do. Source: Internet
Although the galactic vector potential is very large because the galactic magnetic field exists on very great length scales, only the magnetic field would be observable if the photon is massless. Source: Internet
Also known as 'sticky particles', massless gluons are described as a complicated version of the photon, because just like how photons are responsible for exerting the force of electromagnetism, gluons are in charge of exerting a strong nuclear force. Source: Internet
From cosmological arguments, relic background neutrinos are estimated to have density of 56 of each type per cubic centimeter and temperature main (main) if they are massless, much colder if their mass exceeds main. Source: Internet
E.g., Appendix XXXII in citation Experimental checks on photon mass Current commonly accepted physical theories imply or assume the photon to be strictly massless. Source: Internet