demon

Etymology 1

being tormented by demons in The Torment of Saint Anthony, by Michelangelo (c. 1487).]] From Middle English demon, a borrowing from Medieval Latin dēmōn, daemōn (“lar, familiar spirit, guardian spirit”), from Ancient Greek δαίμων (daímōn, “dispenser, god, protective spirit”). Doublet of daimon.

noun

1. An evil supernatural spirit.
   1. An evil spirit resident in or working for Hell; a devil.
   2. (now chiefly historical) A false god or idol; a Satanic divinity.
   3. A very wicked or malevolent person; also (in weakened sense) a mischievous person, especially a child.
   4. A source (especially personified) of great evil or wickedness; a destructive feeling or character flaw.
      The demon of stupidity haunts me whenever I open my mouth.
   5. (in the plural) A person's fears or anxieties.
      After a short spell on an adult psychiatric ward, she decided to find her own way to deal with her demons. 21 January 2013, The Guardian
2. A neutral supernatural spirit.
   1. A person's inner spirit or genius; a guiding or creative impulse.
      “You saw her. And I picked her up,” Lyra said, blushing, because of course it was a gross violation of manners to touch something so private as someone else's dæmon. 2000, Phillip Pullman, The Amber Spyglass
   2. (Greek mythology) A tutelary deity or spirit intermediate between the major Olympian gods and mankind, especially a deified hero or the entity which supposedly guided Socrates, telling him what not to do.
   3. A spirit not considered to be inherently evil; a (non-Christian) deity or supernatural being.
   4. A hypothetical entity with special abilities postulated for the sake of a thought experiment in philosophy or physics.
      Let the orders now be that each demon is to stop all molecules from crossing his area in either direction except 100 coming from A, arbitrarily chosen to be let pass into B, and a greater number, having among them less energy but equal momentum, to cross from B to A. 1874, William Thomson, 1st Baron Kelvin, “Kinetic Theory of the Dissipation of Energy” in Nature 9, 441-444
3. Someone with great strength, passion or skill for a particular activity, pursuit etc.; an enthusiast.
   He’s a demon at the card tables.
   Chelsea defended like demons to snuff out Manchester City but this was a perfectly calibrated triumph, built upon a structured attacking approach, choosing the right moments to transition, and illuminated by the smoothness of Havertz’s technique. May 29 2021, David Hytner, “Chelsea win Champions League after Kai Havertz stuns Manchester City”, in The Guardian
4. (card games) A type of patience or solitaire (card game) played in the UK and/or US.
   Coordinate term: Canfield
   ‘That's much the best feeling to have.’ She dealt out the first row of ‘demon’. 1924, EM Forster, A Passage to India, Penguin, published 2005, page 89
5. Any of various hesperiid butterflies of the genera Notocrypta and Udaspes.

Etymology 2

distinct electron motion + -on

noun

1. (physics) Acronym of distinct electron motion particle.: A quasiparticle, a type of massless neutral electron excitation associated with superconductivity.