Monomania \mon-uh-MAY-nee-uh; -nyuh\, noun:
1. Pathological obsession with a single subject or idea.
2. Excessive concentration of interest upon one particular subject or idea.

One of the themes in the book was the necessity for a leader to be passionate about the work. And sometimes in a corporate setting, passion becomes monomania.
— “Balancing the Personal and the Professional”, New York Times, October 10, 1999

It is a monomania that approaches a frenzy in which girlfriends or wife, family and sleep, mean nothing.
— Newgate Callendar, “Crime”, New York Times, January 4, 1987

He was . . . a rather impossible person — self-absorbed to the point of monomania (when lesser beings presumed to take part in his monologues, he would say “Quite” and then continue along his solitary path).
— Thomas M. Disch, “Later Auden”, Washington Post, July 4, 1999

After visiting American prisons Tocqueville and his traveling companion, Gustave de Beaumont, wrote that social reformers in the United States had been swept up in “the monomania of the penitentiary system,” convinced that prisons were “a remedy for all the evils of society.”
— Eric Schlosser, “The Prison-Industrial Complex”, The Atlantic, December 1998

Monomania is derived from the Greek elements mono-, “one, single, alone” + mania, “madness, frenzy, enthusiasm.” Entry and Pronunciation for monomania

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