XEUV

The term XEUV is used in astrophysics for an EMR spectrum-range spanning extreme ultraviolet (EUV) plus some or all the X-ray range, definitely including its less energetic portion (soft X-rays). Papers using the term do not always specify the exact range they mean, but when specified, the lower-wavelength bound is generally in the 0.1 and 0.2 nm range. However, the term may sometimes be intended to cover much or all of X-rays and/or ultraviolet.

The term is useful because any defined boundary between UV and X-rays is arbitrary. Given the (somewhat-consensus) boundary of 10 nm (or any other defined boundary), there would be sources emitting EMR on both sides of the boundary, some effects such as photoevaporation would result from EMR on both sides, and some optics techniques (e.g., sensing instruments) would be applicable to both.