arcana

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ar·ca·num

A0402400 (är-kā′nəm)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.]

arcana

(ɑːˈkeɪnə; -ˈkɑː-) n (Alternative Belief Systems) either of the two divisions (the minor arcana and the major arcana) of a pack of tarot cards