demon

Less common meanings

6. 6
   thought experimentnouncountable

   A hypothetical being with special abilities, imagined to explore an idea in a philosophical or physical thought experiment.

   Maxwell's thought experiment features a demon that opens a tiny door to separate hot and cold molecules.

   Descartes imagined a deceiving demon to question whether anything could be known for certain.

   Note

   Physics and philosophy borrowed a spirit to stand for an impossible agent. Maxwell's demon is the best known. William Thomson, Lord Kelvin, wrote in 1874 of whole squads of them, each ordered "to stop all molecules from crossing his area" except a chosen few. Such a demon is a device for testing a law, not an object of belief, and its powers are stipulated rather than explained. Source

   Checked 30 Oct 2026 · 8 facts

   • The thought-experiment sense borrows the idea of a supernatural spirit. en.wikipedia.org
   • Maxwell's demon is the best-known example. math.mit.edu
   • William Thomson was also known as Lord Kelvin. en.wikipedia.org
   • Thomson's discussion was published in 1874. nature.com
   • Thomson imagined an army of demons. philocosmology.rutgers.edu
   • The quotation is exact; Thomson's instructions permit selected molecules to cross. philocosmology.rutgers.edu
   • The demon is an imagined agent used to examine a physical law. math.mit.edu
   • The demon's abilities are stipulated as assumptions. philocosmology.rutgers.edu
7. 7
   inspirationnouncountable

   The inner spirit or genius that drives someone, guiding them or prompting their creativity.

   The poet credited a restless demon for his sudden bursts of inspiration.

   A creative demon seemed to guide every brushstroke she made.

   Similarmuse, genius, spirit

   Note

   The older, kinder spirit that keeps a person. Shakespeare's Antony is told that "thy Dæmon that thy spirit which keepes thee" is noble and courageous. The spellings dæmon and daemon often mark this sense. Philip Pullman's His Dark Materials novels build a world on it, and in The Amber Spyglass (2000) each person's dæmon is so private that touching another's is a gross violation of manners. Source

   Checked 30 Oct 2026 · 5 facts

   • An older conception of the demon is a benevolent guardian spirit. en.wikipedia.org
   • In Shakespeare's Antony and Cleopatra, the Soothsayer tells Antony that his guardian spirit is noble and courageous; the quoted wording matches the First Folio. en.wikisource.org
   • Philip Pullman wrote His Dark Materials, whose dæmons embody a person's inner self. en.wikipedia.org
   • The Amber Spyglass was first published in 2000. en.wikipedia.org
   • The Amber Spyglass describes touching someone else's dæmon as a gross violation of manners because it is intensely private. uacademic.info
8. 8
   card gamenoununcountable

   A type of patience or solitaire card game, played by one person, known in the UK and the US.

   On rainy afternoons my grandmother would play demon for hours.

   A single game of demon rarely comes out, which is part of its appeal.

   UsageNo article, like other game names: play demon.

   Note

   Americans know the same game as Canfield. A packet of thirteen cards, itself called the demon, must be played out, and the game is rarely won. E. M. Forster's A Passage to India (1924) has a character who "dealt out the first row of 'demon'." Source

   Checked 1 Nov 2026 · 5 facts

   • The game called demon in Britain is called Canfield in the United States. en.wikipedia.org
   • The game has a thirteen-card reserve called the demon, which must be cleared to win. en.wikipedia.org
   • The game is rarely won under ordinary playing conditions. en.wikipedia.org
   • E. M. Forster's A Passage to India was first published in 1924. openlibrary.org
   • The narrator describes Mrs. Moore dealing the first row of demon, with the game's name in inverted commas. gutenberg.org
9. 9
   noun

   Any of several closely related skipper butterflies of tropical Asia and Australasia known as demons, such as those of the genus Notocrypta and the grass demon (Ancistroides folus).
10. 10
    noun

    In physics, a neutral collective excitation in a metal, in which electrons in different energy bands move out of phase; the name joins distinct electron motion (D.E.M.) with the particle ending -on.