An invisible Electromagnetic radiation (also called solar radiation) whose wavelength is shorter than visible light but greater than X-rays (i.e in ORDER of 10-8 m) is called ultraviolet wave.
From the related links: between about 10 nanometers (most energetic Extreme Ultraviolet) to about 300 nanometers (least energetic Near Ultraviolet). Visible violet light is about 400 nanometers.