Roentgen ray and Roentgen rays

Roentgen ray noun - Electromagnetic radiation of short wavelength produced when high-speed electrons strike a solid target.

Roentgen rays and roentgen ray are semantically related. in picture of inside a body topic. In some cases you can use "Roentgen rays" instead a noun phrase "Roentgen ray".

Roentgen ray and Roentgen rays are semantically related. Sometimes you can replace phrase "Roentgen ray" with "Roentgen rays", this phrases are similar.