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x-ray or X-ray (ĕksrā′)
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n. or x ray or X ray
1.
a. A photon of electromagnetic radiation of very short wavelength, ranging from about 10 down to 0.01 nanometers, and very high energy, ranging from about 100 up to 100,000 electron volts.
b. often x-rays or X-rays A narrow beam of such photons. X-rays are used for their penetrating power in radiography, radiology, radiotherapy, and scientific research. Also called roentgen ray.
2.
a. A photograph taken with x-rays.
b. The act or process of taking such a photograph: Did the patient move during the x-ray?
tr.v. x-rayed, x-ray·ing, x-rays or X-rayed or X-ray·ing or X-rays
1. To irradiate with x-rays.
2. To photograph with x-rays.
[From translation of obsolete German X-Strahlen, x-rays (coined by their discoverer Wilhelm Conrad Roentgen ) : x, x, unknown factor (since x-rays were a previously unknown form of radiation) + Strahlen, pl. of Strahle, ray.]
(click for a larger image)
x-ray
of an adult human hand
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.
 

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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