What's The Difference Between UV Light & UV-C Light?

(Source: https://commons.wikimedia.org)

Ultraviolet (UV) light refers to the region of the electromagnetic spectrum between visible light and X-rays, with a wavelength ranging between 10nm to 400nm.

It is not visible to the human eye, because it has a shorter wavelength and higher frequency than the light our brain perceives as images.

There are three types of UV rays, namely UV-A, UV-B and UV-C, which are classified according to their wavelength ranges. Of the three, UV-A has the longest wavelength and UV-C has the shortest wavelength.  

UV-A: 315nm-400nm
UV-B: 280nm-315nm
UV-C: 100nm-280nm

UV-C is also known as "germicidal UV", and is commonly used for disinfection as it demonstrates significant germicidal properties.

In short, UV-C light is a subset of UV light...and to be even more specific, UV-C light is the shortest-wavelength variant of the three categories of UV light wavelengths.