1. The branch of medicine that deals with diagnostic images of anatomic structures made through the use of electromagnetic radiation or sound waves and that treats disease through the use of radioactive compounds. Radiological imaging techniques include x-rays, CT scans, PET scans, MRIs, and ultrasonograms.
2. The use of radiation for the scientific examination of material structures; radioscopy.
ra′di·o·logi·cal (-ə-lŏjĭ-kəl), ra′di·o·logic (-lŏjĭk) adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. 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:
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.