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o·id·i·um

(ō-ĭdē-əm)

n. pl. o·id·i·a (-ē-ə)

1. A thin-walled spore produced asexually by fragmentation in certain filamentous fungi.

2. Any of various fungi that cause powdery mildew.

[New Latin Ōidium, fungus genus, from Greek ōion, egg; see OO-.]

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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