In my opinion, a light ray is the part of the electromagnetic spectrum which can be seen by the eye.
You get a light ray as you do a gamma ray, X ray, heat ray, UV ray etc.
Light is used to define a certain frequency range or wavelength range of the electromagnetic spectrum, much in the same way that X ray, Gamma ray, Radio wave etc are used to define other frequency/wavelength ranges of the electromagnetic spectrum.
The electromagnetic spectrum has behavioural aspects of both a wave and a particle, the lower the frequency the more like a wave it behaves (Long wave radio is great at bending round buildings etc much better than shortwave), the higher, then the more like a particle it behaves (Gamma rays are destructive). Perhaps this is why radio waves are referred to as a wave rather than a ray (Just a wee thought I had)
Going by that I would say that light just refers to a part of the electromagnetic spectrum ie in the wavelenghth range of 400 to 700 nanometres in the same way that X rays, Gamma rays etc are other parts of the electromagnetic spectrum.
Some poeple generalise and say that X rays etc are another form of light, it is light with a different frequency however you don't hear many poeple saying that light is another form of Gamma Ray.
This is more true of parts of the electromagnetic spectrum with a frequency very close to that of light, ie Infra red and Ultra violet, they are reffered to as forms of light far more than Gamma rays ie Ultra violet light.
The common thing among them is that they are all parts of the electromagnetic spectrum. I went online and typed; define light. Not all but most definitions said "that can be seen by the human eye or by animals".
