e·ti·ol·o·gy also ae·ti·ol·o·gy (ē′tē-ŏlə-jē)
n. pl. e·ti·ol·o·gies also ae·ti·ol·o·gies
a. The study of causes or origins.
b. The branch of medicine that deals with the causes or origins of disease.
a. Assignment of a cause, an origin, or a reason for something.
b. The cause or origin of a disease or disorder as determined by medical diagnosis.
[Late Latin aetiologia, from Greek aitiologiā : aitiā, cause + -logiā, -logy.]
e′ti·o·logic (-ə-lŏjĭk), e′ti·o·logi·cal 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.