n. pl. ar·ca·na (-nə) or ar·ca·nums
1. A deep secret; a mystery.
2. often arcana Specialized knowledge or details unknown to or misunderstood by the average person: "a private-equity investor whose specialty was the arcana of the banking industry" (Andrew Ross Sorkin).
3. A secret essence or remedy; an elixir.
[Latin arcānum, from neuter of arcānus, secret; see ARCANE.]
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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.