on·col·o·gy (ŏn-kŏlə-jē, ŏng-)
The branch of medicine that deals with tumors, including study of their development, diagnosis, treatment, and prevention.
on′co·logi·cal (-kə-lŏjĭ-kəl), on′co·logic (-lŏjĭk) adj.
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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.