n. pl. e·pen·the·ses (-sēz′)
The insertion of a sound in the middle of a word, as in Middle English thunder from Old English thunor.
[Late Latin, from Greek, from epentithenai, to insert : ep-, epi-, epi- + en-, in; see EN-2 + tithenai, to place; see dhē- in the Appendix of Indo-European roots.]
ep′en·thetic (ĕp′ĭn-thĕtĭk) 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.