Ultraviolet a. : Lying outside the visible spectrum at its violet end; -- said of rays more refrangible than the extreme violet rays of the spectrum.

Example:
What's a good way to take Ultraviolet pictures?

Taxonomy
UV, UV light, UV radiation, skin, wavelengths, sunscreen, UVA, ultraviolet light, UVB, visible light, sunlight, lamps, eV, black light, ultraviolet radiation, DNA damage, exposure, DNA.

Defination from the web:
Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 ... In photolithography and laser technology, the term deep ultraviolet or DUV refers to wavelengths below 300 nm. ...